Merge #20305: wallet: introduce fee_rate sat/vB param/option

05e82d86b09d914ebce05dbc92a7299cb026847b wallet: override minfee checks (fOverrideFeeRate) for fee_rate (Jon Atack)
9a670b4f07a6140de809d73cbd7f3e614eb6ea74 wallet: update sendtoaddress, send RPC examples with fee_rate (Jon Atack)
be481b72e24fb6834bd674cd8daee67c6938b42d wallet: use MIN_RELAY_TX_FEE in bumpfee help (Jon Atack)
449b730579566459e350703611629e63e54657ed wallet: provide valid values if invalid estimate mode passed (Jon Atack)
6da3afbaee5809ebf6d88efaa3958c505c2d71c7 wallet: update remaining rpcwallet fee rate units to BTC/kvB (Jon Atack)
173b5b5fe07d45be5a1e5bc7a5df996f20ab1e85 wallet: update fee rate units, use sat/vB for fee_rate error messages (Jon Atack)
7f9835a05abf3e168ad93e7195cbaa4bf61b9b07 wallet: remove fee rates from conf_target helps (Jon Atack)
b7994c01e9a3251536fe6538a22f614774eec82d wallet: add fee_rate unit warnings to bumpfee (Jon Atack)
410e471fa42d3db04e8879c71f8c824dcc151a83 wallet: remove redundant bumpfee fee_rate checks (Jon Atack)
a0d495747320c79b27a83c216dcc526ac8df8f24 wallet: introduce fee_rate (sat/vB) param/option (Jon Atack)
e21212f01b7c41eba13b0479b252053cf482bc1f wallet: remove unneeded WALLET_BTC_KB_TO_SAT_B constant (Jon Atack)
6112cf20d43b0be34fe0edce2ac3e6b27cae1bbe wallet: add CFeeRate ctor doxygen documentation (Jon Atack)
3f7279161347543ce4e997d78ea89a4043491145 wallet: fix bug in RPC send options (Jon Atack)

Pull request description:

  This PR builds on #11413 and #20220 to address #19543.

  - replace overloading the conf_target and estimate_mode params with `fee_rate` in sat/vB in the sendtoaddress, sendmany, send, fundrawtransaction, walletcreatefundedpsbt, and bumpfee RPCs

  - allow non-actionable conf_target value of `0` and estimate_mode value of `""` to be passed to use `fee_rate` as a positional argument, in addition to as a named argument

  - fix a bug in the experimental send RPC described in https://github.com/bitcoin/bitcoin/pull/20220#discussion_r513789526 where args were not being passed correctly into the options values

  - update the feerate error message units for these RPCs from BTC/kB to sat/vB

  - update the test coverage, help docs, doxygen docs, and some of the RPC examples

  - other changes to address the excellent review feedback

  See this wallet meeting log for more context: http://www.erisian.com.au/bitcoin-core-dev/log-2020-11-06.html#l-309

ACKs for top commit:
  achow101:
    re-ACK 05e82d8
  MarcoFalke:
    review ACK 05e82d86b0 did not test and found a few style nits, which can be fixed later 🍯
  Xekyo:
    tACK 05e82d86b09d914ebce05dbc92a7299cb026847b
  Sjors:
    utACK 05e82d86b09d914ebce05dbc92a7299cb026847b

Tree-SHA512: a4ee5f184ada53f1840b2923d25873bda88c5a2ae48e67eeea2417a0b35154798cfdb3c147b05dd56bd6608a784e1b91623bb985ee2ab9ef2baaec22206d0a9c

15 files changed, 447 insertions, 426 deletions

diff --git a/src/policy/feerate.cpp b/src/policy/feerate.cpp
index a01e259731..04e0e117a5 100644
--- a/src/policy/feerate.cpp
+++ b/src/policy/feerate.cpp
@@ -38,7 +38,7 @@ CAmount CFeeRate::GetFee(size_t nBytes_) const
 std::string CFeeRate::ToString(const FeeEstimateMode& fee_estimate_mode) const
 {
     switch (fee_estimate_mode) {
-    case FeeEstimateMode::SAT_B:  return strprintf("%d.%03d %s/B", nSatoshisPerK / 1000, nSatoshisPerK % 1000, CURRENCY_ATOM);
-    default:                      return strprintf("%d.%08d %s/kB", nSatoshisPerK / COIN, nSatoshisPerK % COIN, CURRENCY_UNIT);
+    case FeeEstimateMode::SAT_VB: return strprintf("%d.%03d %s/vB", nSatoshisPerK / 1000, nSatoshisPerK % 1000, CURRENCY_ATOM);
+    default:                      return strprintf("%d.%08d %s/kvB", nSatoshisPerK / COIN, nSatoshisPerK % COIN, CURRENCY_UNIT);
     }
 }
diff --git a/src/policy/feerate.h b/src/policy/feerate.h
index 883940f73c..7c5660ac8a 100644
--- a/src/policy/feerate.h
+++ b/src/policy/feerate.h
@@ -19,8 +19,8 @@ enum class FeeEstimateMode {
     UNSET,        //!< Use default settings based on other criteria
     ECONOMICAL,   //!< Force estimateSmartFee to use non-conservative estimates
     CONSERVATIVE, //!< Force estimateSmartFee to use conservative estimates
-    BTC_KB,       //!< Use explicit BTC/kB fee given in coin control
-    SAT_B,        //!< Use explicit sat/B fee given in coin control
+    BTC_KVB,      //!< Use BTC/kvB fee rate unit
+    SAT_VB,       //!< Use sat/vB fee rate unit
 };
 
 /**
@@ -39,7 +39,16 @@ public:
         // We've previously had bugs creep in from silent double->int conversion...
         static_assert(std::is_integral<I>::value, "CFeeRate should be used without floats");
     }
-    /** Constructor for a fee rate in satoshis per kB. The size in bytes must not exceed (2^63 - 1)*/
+    /** Constructor for a fee rate in satoshis per kvB (sat/kvB). The size in bytes must not exceed (2^63 - 1).
+     *
+     *  Passing an nBytes value of COIN (1e8) returns a fee rate in satoshis per vB (sat/vB),
+     *  e.g. (nFeePaid * 1e8 / 1e3) == (nFeePaid / 1e5),
+     *  where 1e5 is the ratio to convert from BTC/kvB to sat/vB.
+     *
+     *  @param[in] nFeePaid  CAmount fee rate to construct with
+     *  @param[in] nBytes    size_t bytes (units) to construct with
+     *  @returns   fee rate
+     */
     CFeeRate(const CAmount& nFeePaid, size_t nBytes);
     /**
      * Return the fee in satoshis for the given size in bytes.
@@ -56,7 +65,7 @@ public:
     friend bool operator>=(const CFeeRate& a, const CFeeRate& b) { return a.nSatoshisPerK >= b.nSatoshisPerK; }
     friend bool operator!=(const CFeeRate& a, const CFeeRate& b) { return a.nSatoshisPerK != b.nSatoshisPerK; }
     CFeeRate& operator+=(const CFeeRate& a) { nSatoshisPerK += a.nSatoshisPerK; return *this; }
-    std::string ToString(const FeeEstimateMode& fee_estimate_mode = FeeEstimateMode::BTC_KB) const;
+    std::string ToString(const FeeEstimateMode& fee_estimate_mode = FeeEstimateMode::BTC_KVB) const;
 
     SERIALIZE_METHODS(CFeeRate, obj) { READWRITE(obj.nSatoshisPerK); }
 };
diff --git a/src/rpc/client.cpp b/src/rpc/client.cpp
index 88c8ebe1f6..042005b9a6 100644
--- a/src/rpc/client.cpp
+++ b/src/rpc/client.cpp
@@ -41,7 +41,8 @@ static const CRPCConvertParam vRPCConvertParams[] =
     { "sendtoaddress", 5 , "replaceable" },
     { "sendtoaddress", 6 , "conf_target" },
     { "sendtoaddress", 8, "avoid_reuse" },
-    { "sendtoaddress", 9, "verbose"},
+    { "sendtoaddress", 9, "fee_rate"},
+    { "sendtoaddress", 10, "verbose"},
     { "settxfee", 0, "amount" },
     { "sethdseed", 0, "newkeypool" },
     { "getreceivedbyaddress", 1, "minconf" },
@@ -73,7 +74,8 @@ static const CRPCConvertParam vRPCConvertParams[] =
     { "sendmany", 4, "subtractfeefrom" },
     { "sendmany", 5 , "replaceable" },
     { "sendmany", 6 , "conf_target" },
-    { "sendmany", 8, "verbose" },
+    { "sendmany", 8, "fee_rate"},
+    { "sendmany", 9, "verbose" },
     { "deriveaddresses", 1, "range" },
     { "scantxoutset", 1, "scanobjects" },
     { "addmultisigaddress", 0, "nrequired" },
@@ -129,7 +131,8 @@ static const CRPCConvertParam vRPCConvertParams[] =
     { "lockunspent", 1, "transactions" },
     { "send", 0, "outputs" },
     { "send", 1, "conf_target" },
-    { "send", 3, "options" },
+    { "send", 3, "fee_rate"},
+    { "send", 4, "options" },
     { "importprivkey", 2, "rescan" },
     { "importaddress", 2, "rescan" },
     { "importaddress", 3, "p2sh" },
diff --git a/src/rpc/mining.cpp b/src/rpc/mining.cpp
index a561b7e93c..6522c0d73e 100644
--- a/src/rpc/mining.cpp
+++ b/src/rpc/mining.cpp
@@ -1070,7 +1070,7 @@ static RPCHelpMan estimatesmartfee()
     if (!request.params[1].isNull()) {
         FeeEstimateMode fee_mode;
         if (!FeeModeFromString(request.params[1].get_str(), fee_mode)) {
-            throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid estimate_mode parameter");
+            throw JSONRPCError(RPC_INVALID_PARAMETER, InvalidEstimateModeErrorMessage());
         }
         if (fee_mode == FeeEstimateMode::ECONOMICAL) conservative = false;
     }
diff --git a/src/test/amount_tests.cpp b/src/test/amount_tests.cpp
index e20900ed13..c16519a6b1 100644
--- a/src/test/amount_tests.cpp
+++ b/src/test/amount_tests.cpp
@@ -98,7 +98,7 @@ BOOST_AUTO_TEST_CASE(BinaryOperatorTest)
     BOOST_CHECK(a <= a);
     BOOST_CHECK(b >= a);
     BOOST_CHECK(b >= b);
-    // a should be 0.00000002 BTC/kB now
+    // a should be 0.00000002 BTC/kvB now
     a += a;
     BOOST_CHECK(a == b);
 }
@@ -107,7 +107,9 @@ BOOST_AUTO_TEST_CASE(ToStringTest)
 {
     CFeeRate feeRate;
     feeRate = CFeeRate(1);
-    BOOST_CHECK_EQUAL(feeRate.ToString(), "0.00000001 BTC/kB");
+    BOOST_CHECK_EQUAL(feeRate.ToString(), "0.00000001 BTC/kvB");
+    BOOST_CHECK_EQUAL(feeRate.ToString(FeeEstimateMode::BTC_KVB), "0.00000001 BTC/kvB");
+    BOOST_CHECK_EQUAL(feeRate.ToString(FeeEstimateMode::SAT_VB), "0.001 sat/vB");
 }
 
 BOOST_AUTO_TEST_SUITE_END()
diff --git a/src/util/fees.cpp b/src/util/fees.cpp
index 6208a20a97..1855c0bc90 100644
--- a/src/util/fees.cpp
+++ b/src/util/fees.cpp
@@ -40,8 +40,6 @@ const std::vector<std::pair<std::string, FeeEstimateMode>>& FeeModeMap()
         {"unset", FeeEstimateMode::UNSET},
         {"economical", FeeEstimateMode::ECONOMICAL},
         {"conservative", FeeEstimateMode::CONSERVATIVE},
-        {(CURRENCY_UNIT + "/kB"), FeeEstimateMode::BTC_KB},
-        {(CURRENCY_ATOM + "/B"), FeeEstimateMode::SAT_B},
     };
     return FEE_MODES;
 }
@@ -51,6 +49,11 @@ std::string FeeModes(const std::string& delimiter)
     return Join(FeeModeMap(), delimiter, [&](const std::pair<std::string, FeeEstimateMode>& i) { return i.first; });
 }
 
+const std::string InvalidEstimateModeErrorMessage()
+{
+    return "Invalid estimate_mode parameter, must be one of: \"" + FeeModes("\", \"") + "\"";
+}
+
 bool FeeModeFromString(const std::string& mode_string, FeeEstimateMode& fee_estimate_mode)
 {
     auto searchkey = ToUpper(mode_string);
diff --git a/src/util/fees.h b/src/util/fees.h
index d52046a44c..3f1c33ad9c 100644
--- a/src/util/fees.h
+++ b/src/util/fees.h
@@ -13,5 +13,6 @@ enum class FeeReason;
 bool FeeModeFromString(const std::string& mode_string, FeeEstimateMode& fee_estimate_mode);
 std::string StringForFeeReason(FeeReason reason);
 std::string FeeModes(const std::string& delimiter);
+const std::string InvalidEstimateModeErrorMessage();
 
 #endif // BITCOIN_UTIL_FEES_H
diff --git a/src/wallet/rpcwallet.cpp b/src/wallet/rpcwallet.cpp
index 8b08d7a5e6..6efa3d0c27 100644
--- a/src/wallet/rpcwallet.cpp
+++ b/src/wallet/rpcwallet.cpp
@@ -29,6 +29,7 @@
 #include <util/translation.h>
 #include <util/url.h>
 #include <util/vector.h>
+#include <validation.h>
 #include <wallet/coincontrol.h>
 #include <wallet/context.h>
 #include <wallet/feebumper.h>
@@ -48,8 +49,6 @@ using interfaces::FoundBlock;
 static const std::string WALLET_ENDPOINT_BASE = "/wallet/";
 static const std::string HELP_REQUIRING_PASSPHRASE{"\nRequires wallet passphrase to be set with walletpassphrase call if wallet is encrypted.\n"};
 
-static const uint32_t WALLET_BTC_KB_TO_SAT_B = COIN / 1000; // 1 sat / B = 0.00001 BTC / kB
-
 static inline bool GetAvoidReuseFlag(const CWallet* const pwallet, const UniValue& param) {
     bool can_avoid_reuse = pwallet->IsWalletFlagSet(WALLET_FLAG_AVOID_REUSE);
     bool avoid_reuse = param.isNull() ? can_avoid_reuse : param.get_bool();
@@ -199,36 +198,44 @@ static std::string LabelFromValue(const UniValue& value)
 /**
  * Update coin control with fee estimation based on the given parameters
  *
- * @param[in]     pwallet        Wallet pointer
- * @param[in,out] cc             Coin control which is to be updated
- * @param[in]     estimate_mode  String value (e.g. "ECONOMICAL")
- * @param[in]     estimate_param Parameter (blocks to confirm, explicit fee rate, etc)
- * @throws a JSONRPCError if estimate_mode is unknown, or if estimate_param is missing when required
+ * @param[in]     pwallet           Wallet pointer
+ * @param[in,out] cc                Coin control to be updated
+ * @param[in]     conf_target       UniValue integer; confirmation target in blocks, values between 1 and 1008 are valid per policy/fees.h;
+ *                                      if a fee_rate is present, 0 is allowed here as a no-op positional placeholder
+ * @param[in]     estimate_mode     UniValue string; fee estimation mode, valid values are "unset", "economical" or "conservative";
+ *                                      if a fee_rate is present, "" is allowed here as a no-op positional placeholder
+ * @param[in]     fee_rate          UniValue real; fee rate in sat/vB;
+ *                                      if a fee_rate is present, both conf_target and estimate_mode must either be null, or no-op
+ * @param[in]     override_min_fee  bool; whether to set fOverrideFeeRate to true to disable minimum fee rate checks and instead
+ *                                      verify only that fee_rate is greater than 0
+ * @throws a JSONRPCError if conf_target, estimate_mode, or fee_rate contain invalid values or are in conflict
  */
-static void SetFeeEstimateMode(const CWallet* pwallet, CCoinControl& cc, const UniValue& estimate_mode, const UniValue& estimate_param)
+static void SetFeeEstimateMode(const CWallet* pwallet, CCoinControl& cc, const UniValue& conf_target, const UniValue& estimate_mode, const UniValue& fee_rate, bool override_min_fee)
 {
-    if (!estimate_mode.isNull()) {
-        if (!FeeModeFromString(estimate_mode.get_str(), cc.m_fee_mode)) {
-            throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid estimate_mode parameter");
+    if (!fee_rate.isNull()) {
+        if (!conf_target.isNull() && conf_target.get_int() > 0) {
+            throw JSONRPCError(RPC_INVALID_PARAMETER, "Cannot specify both conf_target and fee_rate. Please provide either a confirmation target in blocks for automatic fee estimation, or an explicit fee rate.");
         }
-    }
-
-    if (cc.m_fee_mode == FeeEstimateMode::BTC_KB || cc.m_fee_mode == FeeEstimateMode::SAT_B) {
-        if (estimate_param.isNull()) {
-            throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("Selected estimate_mode %s requires a fee rate to be specified in conf_target", estimate_mode.get_str()));
+        if (!estimate_mode.isNull() && !estimate_mode.get_str().empty()) {
+            throw JSONRPCError(RPC_INVALID_PARAMETER, "Cannot specify both estimate_mode and fee_rate");
         }
-
-        CAmount fee_rate = AmountFromValue(estimate_param);
-        if (cc.m_fee_mode == FeeEstimateMode::SAT_B) {
-            fee_rate /= WALLET_BTC_KB_TO_SAT_B;
+        CFeeRate fee_rate_in_sat_vb{CFeeRate(AmountFromValue(fee_rate), COIN)};
+        if (override_min_fee) {
+            if (fee_rate_in_sat_vb <= CFeeRate(0)) {
+                throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("Invalid fee_rate %s (must be greater than 0)", fee_rate_in_sat_vb.ToString(FeeEstimateMode::SAT_VB)));
+            }
+            cc.fOverrideFeeRate = true;
         }
-
-        cc.m_feerate = CFeeRate(fee_rate);
-
-        // default RBF to true for explicit fee rate modes
+        cc.m_feerate = fee_rate_in_sat_vb;
+        // Default RBF to true for explicit fee_rate, if unset.
         if (cc.m_signal_bip125_rbf == nullopt) cc.m_signal_bip125_rbf = true;
-    } else if (!estimate_param.isNull()) {
-        cc.m_confirm_target = ParseConfirmTarget(estimate_param, pwallet->chain().estimateMaxBlocks());
+        return;
+    }
+    if (!estimate_mode.isNull() && !FeeModeFromString(estimate_mode.get_str(), cc.m_fee_mode)) {
+        throw JSONRPCError(RPC_INVALID_PARAMETER, InvalidEstimateModeErrorMessage());
+    }
+    if (!conf_target.isNull()) {
+        cc.m_confirm_target = ParseConfirmTarget(conf_target, pwallet->chain().estimateMaxBlocks());
     }
 }
 
@@ -441,12 +448,12 @@ static RPCHelpMan sendtoaddress()
                     {"subtractfeefromamount", RPCArg::Type::BOOL, /* default */ "false", "The fee will be deducted from the amount being sent.\n"
                                          "The recipient will receive less bitcoins than you enter in the amount field."},
                     {"replaceable", RPCArg::Type::BOOL, /* default */ "wallet default", "Allow this transaction to be replaced by a transaction with higher fees via BIP 125"},
-                    {"conf_target", RPCArg::Type::NUM, /* default */ "wallet -txconfirmtarget", "Confirmation target (in blocks)\n"
-                                         "or fee rate (for " + CURRENCY_UNIT + "/kB and " + CURRENCY_ATOM + "/B estimate modes)"},
+                    {"conf_target", RPCArg::Type::NUM, /* default */ "wallet -txconfirmtarget", "Confirmation target in blocks"},
                     {"estimate_mode", RPCArg::Type::STR, /* default */ "unset", std::string() + "The fee estimate mode, must be one of (case insensitive):\n"
             "       \"" + FeeModes("\"\n\"") + "\""},
                     {"avoid_reuse", RPCArg::Type::BOOL, /* default */ "true", "(only available if avoid_reuse wallet flag is set) Avoid spending from dirty addresses; addresses are considered\n"
                                          "dirty if they have previously been used in a transaction."},
+                    {"fee_rate", RPCArg::Type::AMOUNT, /* default */ "not set, fall back to wallet fee estimation", "Specify a fee rate in " + CURRENCY_ATOM + "/vB."},
                     {"verbose", RPCArg::Type::BOOL, /* default */ "false", "If true, return extra information about the transaction."},
                 },
                 {
@@ -462,12 +469,17 @@ static RPCHelpMan sendtoaddress()
                     },
                 },
                 RPCExamples{
-                    HelpExampleCli("sendtoaddress", "\"" + EXAMPLE_ADDRESS[0] + "\" 0.1")
-            + HelpExampleCli("sendtoaddress", "\"" + EXAMPLE_ADDRESS[0] + "\" 0.1 \"donation\" \"seans outpost\"")
-            + HelpExampleCli("sendtoaddress", "\"" + EXAMPLE_ADDRESS[0] + "\" 0.1 \"\" \"\" true")
-            + HelpExampleCli("sendtoaddress", "\"" + EXAMPLE_ADDRESS[0] + "\" 0.1 \"\" \"\" false true 0.00002 " + (CURRENCY_UNIT + "/kB"))
-            + HelpExampleCli("sendtoaddress", "\"" + EXAMPLE_ADDRESS[0] + "\" 0.1 \"\" \"\" false true 2 " + (CURRENCY_ATOM + "/B"))
-            + HelpExampleRpc("sendtoaddress", "\"" + EXAMPLE_ADDRESS[0] + "\", 0.1, \"donation\", \"seans outpost\"")
+                    "\nSend 0.1 BTC\n"
+                    + HelpExampleCli("sendtoaddress", "\"" + EXAMPLE_ADDRESS[0] + "\" 0.1") +
+                    "\nSend 0.1 BTC with a confirmation target of 6 blocks in economical fee estimate mode using positional arguments\n"
+                    + HelpExampleCli("sendtoaddress", "\"" + EXAMPLE_ADDRESS[0] + "\" 0.1 \"donation\" \"sean's outpost\" false true 6 economical") +
+                    "\nSend 0.1 BTC with a fee rate of 1 " + CURRENCY_ATOM + "/vB, subtract fee from amount, BIP125-replaceable, using positional arguments\n"
+                    + HelpExampleCli("sendtoaddress", "\"" + EXAMPLE_ADDRESS[0] + "\" 0.1 \"drinks\" \"room77\" true true 0 \"\" 1") +
+                    "\nSend 0.2 BTC with a confirmation target of 6 blocks in economical fee estimate mode using named arguments\n"
+                    + HelpExampleCli("-named sendtoaddress", "address=\"" + EXAMPLE_ADDRESS[0] + "\" amount=0.2 conf_target=6 estimate_mode=\"economical\"") +
+                    "\nSend 0.5 BTC with a fee rate of 25 " + CURRENCY_ATOM + "/vB using named arguments\n"
+                    + HelpExampleCli("-named sendtoaddress", "address=\"" + EXAMPLE_ADDRESS[0] + "\" amount=0.5 fee_rate=25")
+                    + HelpExampleCli("-named sendtoaddress", "address=\"" + EXAMPLE_ADDRESS[0] + "\" amount=0.5 fee_rate=25 subtractfeefromamount=false replaceable=true avoid_reuse=true comment=\"2 pizzas\" comment_to=\"jeremy\" verbose=true")
                 },
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
 {
@@ -502,7 +514,7 @@ static RPCHelpMan sendtoaddress()
     // We also enable partial spend avoidance if reuse avoidance is set.
     coin_control.m_avoid_partial_spends |= coin_control.m_avoid_address_reuse;
 
-    SetFeeEstimateMode(pwallet, coin_control, request.params[7], request.params[6]);
+    SetFeeEstimateMode(pwallet, coin_control, /* conf_target */ request.params[6], /* estimate_mode */ request.params[7], /* fee_rate */ request.params[9], /* override_min_fee */ false);
 
     EnsureWalletIsUnlocked(pwallet);
 
@@ -516,7 +528,7 @@ static RPCHelpMan sendtoaddress()
 
     std::vector<CRecipient> recipients;
     ParseRecipients(address_amounts, subtractFeeFromAmount, recipients);
-    bool verbose = request.params[9].isNull() ? false: request.params[9].get_bool();
+    const bool verbose{request.params[10].isNull() ? false : request.params[10].get_bool()};
 
     return SendMoney(pwallet, coin_control, recipients, mapValue, verbose);
 },
@@ -870,10 +882,10 @@ static RPCHelpMan sendmany()
                         },
                     },
                     {"replaceable", RPCArg::Type::BOOL, /* default */ "wallet default", "Allow this transaction to be replaced by a transaction with higher fees via BIP 125"},
-                    {"conf_target", RPCArg::Type::NUM, /* default */ "wallet -txconfirmtarget", "Confirmation target (in blocks)\n"
-                                       "or fee rate (for " + CURRENCY_UNIT + "/kB and " + CURRENCY_ATOM + "/B estimate modes)"},
+                    {"conf_target", RPCArg::Type::NUM, /* default */ "wallet -txconfirmtarget", "Confirmation target in blocks"},
                     {"estimate_mode", RPCArg::Type::STR, /* default */ "unset", std::string() + "The fee estimate mode, must be one of (case insensitive):\n"
             "       \"" + FeeModes("\"\n\"") + "\""},
+                    {"fee_rate", RPCArg::Type::AMOUNT, /* default */ "not set, fall back to wallet fee estimation", "Specify a fee rate in " + CURRENCY_ATOM + "/vB."},
                     {"verbose", RPCArg::Type::BOOL, /* default */ "false", "If true, return extra infomration about the transaction."},
                 },
                 {
@@ -930,11 +942,11 @@ static RPCHelpMan sendmany()
         coin_control.m_signal_bip125_rbf = request.params[5].get_bool();
     }
 
-    SetFeeEstimateMode(pwallet, coin_control, request.params[7], request.params[6]);
+    SetFeeEstimateMode(pwallet, coin_control, /* conf_target */ request.params[6], /* estimate_mode */ request.params[7], /* fee_rate */ request.params[8], /* override_min_fee */ false);
 
     std::vector<CRecipient> recipients;
     ParseRecipients(sendTo, subtractFeeFromAmount, recipients);
-    bool verbose = request.params[8].isNull() ? false : request.params[8].get_bool();
+    const bool verbose{request.params[9].isNull() ? false : request.params[9].get_bool()};
 
     return SendMoney(pwallet, coin_control, recipients, std::move(mapValue), verbose);
 },
@@ -2311,7 +2323,7 @@ static RPCHelpMan settxfee()
                 "\nSet the transaction fee per kB for this wallet. Overrides the global -paytxfee command line parameter.\n"
                 "Can be deactivated by passing 0 as the fee. In that case automatic fee selection will be used by default.\n",
                 {
-                    {"amount", RPCArg::Type::AMOUNT, RPCArg::Optional::NO, "The transaction fee in " + CURRENCY_UNIT + "/kB"},
+                    {"amount", RPCArg::Type::AMOUNT, RPCArg::Optional::NO, "The transaction fee in " + CURRENCY_UNIT + "/kvB"},
                 },
                 RPCResult{
                     RPCResult::Type::BOOL, "", "Returns true if successful"
@@ -2434,7 +2446,7 @@ static RPCHelpMan getwalletinfo()
                         {RPCResult::Type::NUM, "keypoolsize", "how many new keys are pre-generated (only counts external keys)"},
                         {RPCResult::Type::NUM, "keypoolsize_hd_internal", "how many new keys are pre-generated for internal use (used for change outputs, only appears if the wallet is using this feature, otherwise external keys are used)"},
                         {RPCResult::Type::NUM_TIME, "unlocked_until", /* optional */ true, "the " + UNIX_EPOCH_TIME + " until which the wallet is unlocked for transfers, or 0 if the wallet is locked (only present for passphrase-encrypted wallets)"},
-                        {RPCResult::Type::STR_AMOUNT, "paytxfee", "the transaction fee configuration, set in " + CURRENCY_UNIT + "/kB"},
+                        {RPCResult::Type::STR_AMOUNT, "paytxfee", "the transaction fee configuration, set in " + CURRENCY_UNIT + "/kvB"},
                         {RPCResult::Type::STR_HEX, "hdseedid", /* optional */ true, "the Hash160 of the HD seed (only present when HD is enabled)"},
                         {RPCResult::Type::BOOL, "private_keys_enabled", "false if privatekeys are disabled for this wallet (enforced watch-only wallet)"},
                         {RPCResult::Type::BOOL, "avoid_reuse", "whether this wallet tracks clean/dirty coins in terms of reuse"},
@@ -3047,7 +3059,7 @@ static RPCHelpMan listunspent()
     };
 }
 
-void FundTransaction(CWallet* const pwallet, CMutableTransaction& tx, CAmount& fee_out, int& change_position, const UniValue& options, CCoinControl& coinControl)
+void FundTransaction(CWallet* const pwallet, CMutableTransaction& tx, CAmount& fee_out, int& change_position, const UniValue& options, CCoinControl& coinControl, bool override_min_fee)
 {
     // Make sure the results are valid at least up to the most recent block
     // the user could have gotten from another RPC command prior to now
@@ -3080,7 +3092,8 @@ void FundTransaction(CWallet* const pwallet, CMutableTransaction& tx, CAmount& f
                 {"lockUnspents", UniValueType(UniValue::VBOOL)},
                 {"lock_unspents", UniValueType(UniValue::VBOOL)},
                 {"locktime", UniValueType(UniValue::VNUM)},
-                {"feeRate", UniValueType()}, // will be checked below
+                {"fee_rate", UniValueType()}, // will be checked by AmountFromValue() in SetFeeEstimateMode()
+                {"feeRate", UniValueType()}, // will be checked by AmountFromValue() below
                 {"psbt", UniValueType(UniValue::VBOOL)},
                 {"subtractFeeFromOutputs", UniValueType(UniValue::VARR)},
                 {"subtract_fee_from_outputs", UniValueType(UniValue::VARR)},
@@ -3127,15 +3140,21 @@ void FundTransaction(CWallet* const pwallet, CMutableTransaction& tx, CAmount& f
             lockUnspents = (options.exists("lock_unspents") ? options["lock_unspents"] : options["lockUnspents"]).get_bool();
         }
 
-        if (options.exists("feeRate"))
-        {
+        if (options.exists("feeRate")) {
+            if (options.exists("fee_rate")) {
+                throw JSONRPCError(RPC_INVALID_PARAMETER, "Cannot specify both fee_rate (" + CURRENCY_ATOM + "/vB) and feeRate (" + CURRENCY_UNIT + "/kvB)");
+            }
             if (options.exists("conf_target")) {
-                throw JSONRPCError(RPC_INVALID_PARAMETER, "Cannot specify both conf_target and feeRate");
+                throw JSONRPCError(RPC_INVALID_PARAMETER, "Cannot specify both conf_target and feeRate. Please provide either a confirmation target in blocks for automatic fee estimation, or an explicit fee rate.");
             }
             if (options.exists("estimate_mode")) {
                 throw JSONRPCError(RPC_INVALID_PARAMETER, "Cannot specify both estimate_mode and feeRate");
             }
-            coinControl.m_feerate = CFeeRate(AmountFromValue(options["feeRate"]));
+            CFeeRate fee_rate(AmountFromValue(options["feeRate"]));
+            if (fee_rate <= CFeeRate(0)) {
+                throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("Invalid feeRate %s (must be greater than 0)", fee_rate.ToString(FeeEstimateMode::BTC_KVB)));
+            }
+            coinControl.m_feerate = fee_rate;
             coinControl.fOverrideFeeRate = true;
         }
 
@@ -3145,7 +3164,7 @@ void FundTransaction(CWallet* const pwallet, CMutableTransaction& tx, CAmount& f
         if (options.exists("replaceable")) {
             coinControl.m_signal_bip125_rbf = options["replaceable"].get_bool();
         }
-        SetFeeEstimateMode(pwallet, coinControl, options["estimate_mode"], options["conf_target"]);
+        SetFeeEstimateMode(pwallet, coinControl, options["conf_target"], options["estimate_mode"], options["fee_rate"], override_min_fee);
       }
     } else {
         // if options is null and not a bool
@@ -3202,7 +3221,8 @@ static RPCHelpMan fundrawtransaction()
                                                           "Only solvable inputs can be used. Watch-only destinations are solvable if the public key and/or output script was imported,\n"
                                                           "e.g. with 'importpubkey' or 'importmulti' with the 'pubkeys' or 'desc' field."},
                             {"lockUnspents", RPCArg::Type::BOOL, /* default */ "false", "Lock selected unspent outputs"},
-                            {"feeRate", RPCArg::Type::AMOUNT, /* default */ "not set: makes wallet determine the fee", "Set a specific fee rate in " + CURRENCY_UNIT + "/kB"},
+                            {"fee_rate", RPCArg::Type::AMOUNT, /* default */ "not set, fall back to wallet fee estimation", "Specify a fee rate in " + CURRENCY_ATOM + "/vB."},
+                            {"feeRate", RPCArg::Type::AMOUNT, /* default */ "not set, fall back to wallet fee estimation", "Specify a fee rate in " + CURRENCY_UNIT + "/kvB."},
                             {"subtractFeeFromOutputs", RPCArg::Type::ARR, /* default */ "empty array", "The integers.\n"
                                                           "The fee will be equally deducted from the amount of each specified output.\n"
                                                           "Those recipients will receive less bitcoins than you enter in their corresponding amount field.\n"
@@ -3213,8 +3233,7 @@ static RPCHelpMan fundrawtransaction()
                             },
                             {"replaceable", RPCArg::Type::BOOL, /* default */ "wallet default", "Marks this transaction as BIP125 replaceable.\n"
                                                           "Allows this transaction to be replaced by a transaction with higher fees"},
-                            {"conf_target", RPCArg::Type::NUM, /* default */ "wallet -txconfirmtarget", "Confirmation target (in blocks)\n"
-                                                          "or fee rate (for " + CURRENCY_UNIT + "/kB and " + CURRENCY_ATOM + "/B estimate modes)"},
+                            {"conf_target", RPCArg::Type::NUM, /* default */ "wallet -txconfirmtarget", "Confirmation target in blocks"},
                             {"estimate_mode", RPCArg::Type::STR, /* default */ "unset", std::string() + "The fee estimate mode, must be one of (case insensitive):\n"
                             "       \"" + FeeModes("\"\n\"") + "\""},
                         },
@@ -3266,7 +3285,7 @@ static RPCHelpMan fundrawtransaction()
     CCoinControl coin_control;
     // Automatically select (additional) coins. Can be overridden by options.add_inputs.
     coin_control.m_add_inputs = true;
-    FundTransaction(pwallet, tx, fee, change_position, request.params[1], coin_control);
+    FundTransaction(pwallet, tx, fee, change_position, request.params[1], coin_control, /* override_min_fee */ true);
 
     UniValue result(UniValue::VOBJ);
     result.pushKV("hex", EncodeHexTx(CTransaction(tx)));
@@ -3374,35 +3393,38 @@ RPCHelpMan signrawtransactionwithwallet()
 static RPCHelpMan bumpfee_helper(std::string method_name)
 {
     bool want_psbt = method_name == "psbtbumpfee";
+    const std::string incremental_fee{CFeeRate(DEFAULT_MIN_RELAY_TX_FEE).ToString(FeeEstimateMode::SAT_VB)};
 
     return RPCHelpMan{method_name,
         "\nBumps the fee of an opt-in-RBF transaction T, replacing it with a new transaction B.\n"
         + std::string(want_psbt ? "Returns a PSBT instead of creating and signing a new transaction.\n" : "") +
         "An opt-in RBF transaction with the given txid must be in the wallet.\n"
-        "The command will pay the additional fee by reducing change outputs or adding inputs when necessary. It may add a new change output if one does not already exist.\n"
+        "The command will pay the additional fee by reducing change outputs or adding inputs when necessary.\n"
+        "It may add a new change output if one does not already exist.\n"
         "All inputs in the original transaction will be included in the replacement transaction.\n"
         "The command will fail if the wallet or mempool contains a transaction that spends one of T's outputs.\n"
         "By default, the new fee will be calculated automatically using the estimatesmartfee RPC.\n"
         "The user can specify a confirmation target for estimatesmartfee.\n"
-        "Alternatively, the user can specify a fee_rate (" + CURRENCY_UNIT + " per kB) for the new transaction.\n"
+        "Alternatively, the user can specify a fee rate in " + CURRENCY_ATOM + "/vB for the new transaction.\n"
         "At a minimum, the new fee rate must be high enough to pay an additional new relay fee (incrementalfee\n"
-        "returned by getnetworkinfo) to enter the node's mempool.\n",
+        "returned by getnetworkinfo) to enter the node's mempool.\n"
+        "* WARNING: before version 0.21, fee_rate was in " + CURRENCY_UNIT + "/kvB. As of 0.21, fee_rate is in " + CURRENCY_ATOM + "/vB. *\n",
         {
             {"txid", RPCArg::Type::STR_HEX, RPCArg::Optional::NO, "The txid to be bumped"},
             {"options", RPCArg::Type::OBJ, RPCArg::Optional::OMITTED_NAMED_ARG, "",
                 {
-                    {"conf_target", RPCArg::Type::NUM, /* default */ "wallet -txconfirmtarget", "Confirmation target (in blocks)\n"
-                             "or fee rate (for " + CURRENCY_UNIT + "/kB and " + CURRENCY_ATOM + "/B estimate modes)"},
-                    {"fee_rate", RPCArg::Type::NUM, /* default */ "fall back to 'conf_target'", "fee rate (NOT total fee) to pay, in " + CURRENCY_UNIT + "/kB.\n"
-                             "Specify a fee rate instead of relying on the built-in fee estimator.\n"
-                             "Must be at least 0.0001 " + CURRENCY_UNIT + "/kB higher than the current transaction fee rate.\n"},
+                    {"conf_target", RPCArg::Type::NUM, /* default */ "wallet -txconfirmtarget", "Confirmation target in blocks\n"},
+                    {"fee_rate", RPCArg::Type::AMOUNT, /* default */ "not set, fall back to wallet fee estimation",
+                             "\nSpecify a fee rate in " + CURRENCY_ATOM + "/vB instead of relying on the built-in fee estimator.\n"
+                             "Must be at least " + incremental_fee + " " + CURRENCY_ATOM + "/vB higher than the current transaction fee rate.\n"
+                             "WARNING: before version 0.21, fee_rate was in " + CURRENCY_UNIT + "/kvB. As of 0.21, fee_rate is in " + CURRENCY_ATOM + "/vB.\n"},
                     {"replaceable", RPCArg::Type::BOOL, /* default */ "true", "Whether the new transaction should still be\n"
                              "marked bip-125 replaceable. If true, the sequence numbers in the transaction will\n"
                              "be left unchanged from the original. If false, any input sequence numbers in the\n"
                              "original transaction that were less than 0xfffffffe will be increased to 0xfffffffe\n"
                              "so the new transaction will not be explicitly bip-125 replaceable (though it may\n"
                              "still be replaceable in practice, for example if it has unconfirmed ancestors which\n"
-                             "are replaceable)."},
+                             "are replaceable).\n"},
                     {"estimate_mode", RPCArg::Type::STR, /* default */ "unset", std::string() + "The fee estimate mode, must be one of (case insensitive):\n"
     "         \"" + FeeModes("\"\n\"") + "\""},
                 },
@@ -3455,7 +3477,7 @@ static RPCHelpMan bumpfee_helper(std::string method_name)
             {
                 {"confTarget", UniValueType(UniValue::VNUM)},
                 {"conf_target", UniValueType(UniValue::VNUM)},
-                {"fee_rate", UniValueType(UniValue::VNUM)},
+                {"fee_rate", UniValueType()}, // will be checked by AmountFromValue() in SetFeeEstimateMode()
                 {"replaceable", UniValueType(UniValue::VBOOL)},
                 {"estimate_mode", UniValueType(UniValue::VSTR)},
             },
@@ -3467,22 +3489,10 @@ static RPCHelpMan bumpfee_helper(std::string method_name)
 
         auto conf_target = options.exists("confTarget") ? options["confTarget"] : options["conf_target"];
 
-        if (!conf_target.isNull()) {
-            if (options.exists("fee_rate")) {
-                throw JSONRPCError(RPC_INVALID_PARAMETER, "Cannot specify both conf_target and fee_rate. Please provide either a confirmation target in blocks for automatic fee estimation, or an explicit fee rate.");
-            }
-        } else if (options.exists("fee_rate")) {
-            CFeeRate fee_rate(AmountFromValue(options["fee_rate"]));
-            if (fee_rate <= CFeeRate(0)) {
-                throw JSONRPCError(RPC_INVALID_PARAMETER, strprintf("Invalid fee_rate %s (must be greater than 0)", fee_rate.ToString()));
-            }
-            coin_control.m_feerate = fee_rate;
-        }
-
         if (options.exists("replaceable")) {
             coin_control.m_signal_bip125_rbf = options["replaceable"].get_bool();
         }
-        SetFeeEstimateMode(pwallet, coin_control, options["estimate_mode"], conf_target);
+        SetFeeEstimateMode(pwallet, coin_control, conf_target, options["estimate_mode"], options["fee_rate"], /* override_min_fee */ false);
     }
 
     // Make sure the results are valid at least up to the most recent block
@@ -4018,10 +4028,10 @@ static RPCHelpMan send()
                     },
                 },
             },
-            {"conf_target", RPCArg::Type::NUM, /* default */ "wallet -txconfirmtarget", "Confirmation target (in blocks)\n"
-                    "or fee rate (for " + CURRENCY_UNIT + "/kB and " + CURRENCY_ATOM + "/B estimate modes)"},
+            {"conf_target", RPCArg::Type::NUM, /* default */ "wallet -txconfirmtarget", "Confirmation target in blocks"},
             {"estimate_mode", RPCArg::Type::STR, /* default */ "unset", std::string() + "The fee estimate mode, must be one of (case insensitive):\n"
                         "       \"" + FeeModes("\"\n\"") + "\""},
+            {"fee_rate", RPCArg::Type::AMOUNT, /* default */ "not set, fall back to wallet fee estimation", "Specify a fee rate in " + CURRENCY_ATOM + "/vB."},
             {"options", RPCArg::Type::OBJ, RPCArg::Optional::OMITTED_NAMED_ARG, "",
                 {
                     {"add_inputs", RPCArg::Type::BOOL, /* default */ "false", "If inputs are specified, automatically include more if they are not enough."},
@@ -4029,10 +4039,10 @@ static RPCHelpMan send()
                     {"change_address", RPCArg::Type::STR_HEX, /* default */ "pool address", "The bitcoin address to receive the change"},
                     {"change_position", RPCArg::Type::NUM, /* default */ "random", "The index of the change output"},
                     {"change_type", RPCArg::Type::STR, /* default */ "set by -changetype", "The output type to use. Only valid if change_address is not specified. Options are \"legacy\", \"p2sh-segwit\", and \"bech32\"."},
-                    {"conf_target", RPCArg::Type::NUM, /* default */ "wallet -txconfirmtarget", "Confirmation target (in blocks)\n"
-                            "or fee rate (for " + CURRENCY_UNIT + "/kB and " + CURRENCY_ATOM + "/B estimate modes)"},
+                    {"conf_target", RPCArg::Type::NUM, /* default */ "wallet -txconfirmtarget", "Confirmation target in blocks"},
                     {"estimate_mode", RPCArg::Type::STR, /* default */ "unset", std::string() + "The fee estimate mode, must be one of (case insensitive):\n"
             "       \"" + FeeModes("\"\n\"") + "\""},
+                    {"fee_rate", RPCArg::Type::AMOUNT, /* default */ "not set, fall back to wallet fee estimation", "Specify a fee rate in " + CURRENCY_ATOM + "/vB."},
                     {"include_watching", RPCArg::Type::BOOL, /* default */ "true for watch-only wallets, otherwise false", "Also select inputs which are watch only.\n"
                                           "Only solvable inputs can be used. Watch-only destinations are solvable if the public key and/or output script was imported,\n"
                                           "e.g. with 'importpubkey' or 'importmulti' with the 'pubkeys' or 'desc' field."},
@@ -4069,18 +4079,25 @@ static RPCHelpMan send()
                 }
         },
         RPCExamples{""
-        "\nSend with a fee rate of 1 satoshi per byte\n"
-        + HelpExampleCli("send", "'{\"" + EXAMPLE_ADDRESS[0] + "\": 0.1}' 1 sat/b\n") +
-            "\nCreate a transaction that should confirm the next block, with a specific input, and return result without adding to wallet or broadcasting to the network\n"
+        "\nSend 0.1 BTC with a confirmation target of 6 blocks in economical fee estimate mode\n"
+        + HelpExampleCli("send", "'{\"" + EXAMPLE_ADDRESS[0] + "\": 0.1}' 6 economical\n") +
+        "Send 0.2 BTC with a fee rate of 1 " + CURRENCY_ATOM + "/vB using positional arguments\n"
+        + HelpExampleCli("send", "'{\"" + EXAMPLE_ADDRESS[0] + "\": 0.2}' 0 \"\" 1\n") +
+        "Send 0.2 BTC with a fee rate of 1 " + CURRENCY_ATOM + "/vB using the options argument\n"
+        + HelpExampleCli("send", "'{\"" + EXAMPLE_ADDRESS[0] + "\": 0.2}' '{\"fee_rate\": 1}'\n") +
+        "Send 0.3 BTC with a fee rate of 25 " + CURRENCY_ATOM + "/vB using named arguments\n"
+        + HelpExampleCli("-named send", "outputs='{\"" + EXAMPLE_ADDRESS[0] + "\": 0.3}' fee_rate=25\n") +
+        "Create a transaction that should confirm the next block, with a specific input, and return result without adding to wallet or broadcasting to the network\n"
         + HelpExampleCli("send", "'{\"" + EXAMPLE_ADDRESS[0] + "\": 0.1}' 1 economical '{\"add_to_wallet\": false, \"inputs\": [{\"txid\":\"a08e6907dbbd3d809776dbfc5d82e371b764ed838b5655e72f463568df1aadf0\", \"vout\":1}]}'")
         },
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
         {
             RPCTypeCheck(request.params, {
-                UniValueType(), // ARR or OBJ, checked later
-                UniValue::VNUM,
-                UniValue::VSTR,
-                UniValue::VOBJ
+                UniValueType(), // outputs (ARR or OBJ, checked later)
+                UniValue::VNUM, // conf_target
+                UniValue::VSTR, // estimate_mode
+                UniValue::VNUM, // fee_rate
+                UniValue::VOBJ, // options
                 }, true
             );
 
@@ -4088,18 +4105,28 @@ static RPCHelpMan send()
             if (!wallet) return NullUniValue;
             CWallet* const pwallet = wallet.get();
 
-            UniValue options = request.params[3];
-            if (options.exists("feeRate") || options.exists("fee_rate") || options.exists("estimate_mode") || options.exists("conf_target")) {
+            UniValue options{request.params[4].isNull() ? UniValue::VOBJ : request.params[4]};
+            if (options.exists("conf_target") || options.exists("estimate_mode")) {
                 if (!request.params[1].isNull() || !request.params[2].isNull()) {
-                    throw JSONRPCError(RPC_INVALID_PARAMETER, "Use either conf_target and estimate_mode or the options dictionary to control fee rate");
+                    throw JSONRPCError(RPC_INVALID_PARAMETER, "Pass conf_target and estimate_mode either as arguments or in the options object, but not both");
                 }
             } else {
                 options.pushKV("conf_target", request.params[1]);
                 options.pushKV("estimate_mode", request.params[2]);
             }
+            if (options.exists("fee_rate")) {
+                if (!request.params[3].isNull()) {
+                    throw JSONRPCError(RPC_INVALID_PARAMETER, "Pass the fee_rate either as an argument, or in the options object, but not both");
+                }
+            } else {
+                options.pushKV("fee_rate", request.params[3]);
+            }
             if (!options["conf_target"].isNull() && (options["estimate_mode"].isNull() || (options["estimate_mode"].get_str() == "unset"))) {
                 throw JSONRPCError(RPC_INVALID_PARAMETER, "Specify estimate_mode");
             }
+            if (options.exists("feeRate")) {
+                throw JSONRPCError(RPC_INVALID_PARAMETER, "Use fee_rate (" + CURRENCY_ATOM + "/vB) instead of feeRate");
+            }
             if (options.exists("changeAddress")) {
                 throw JSONRPCError(RPC_INVALID_PARAMETER, "Use change_address");
             }
@@ -4129,7 +4156,7 @@ static RPCHelpMan send()
             // Automatically select coins, unless at least one is manually selected. Can
             // be overridden by options.add_inputs.
             coin_control.m_add_inputs = rawTx.vin.size() == 0;
-            FundTransaction(pwallet, rawTx, fee, change_position, options, coin_control);
+            FundTransaction(pwallet, rawTx, fee, change_position, options, coin_control, /* override_min_fee */ false);
 
             bool add_to_wallet = true;
             if (options.exists("add_to_wallet")) {
@@ -4357,7 +4384,8 @@ static RPCHelpMan walletcreatefundedpsbt()
                             {"change_type", RPCArg::Type::STR, /* default */ "set by -changetype", "The output type to use. Only valid if changeAddress is not specified. Options are \"legacy\", \"p2sh-segwit\", and \"bech32\"."},
                             {"includeWatching", RPCArg::Type::BOOL, /* default */ "true for watch-only wallets, otherwise false", "Also select inputs which are watch only"},
                             {"lockUnspents", RPCArg::Type::BOOL, /* default */ "false", "Lock selected unspent outputs"},
-                            {"feeRate", RPCArg::Type::AMOUNT, /* default */ "not set: makes wallet determine the fee", "Set a specific fee rate in " + CURRENCY_UNIT + "/kB"},
+                            {"fee_rate", RPCArg::Type::AMOUNT, /* default */ "not set, fall back to wallet fee estimation", "Specify a fee rate in " + CURRENCY_ATOM + "/vB."},
+                            {"feeRate", RPCArg::Type::AMOUNT, /* default */ "not set, fall back to wallet fee estimation", "Specify a fee rate in " + CURRENCY_UNIT + "/kvB."},
                             {"subtractFeeFromOutputs", RPCArg::Type::ARR, /* default */ "empty array", "The outputs to subtract the fee from.\n"
                                                           "The fee will be equally deducted from the amount of each specified output.\n"
                                                           "Those recipients will receive less bitcoins than you enter in their corresponding amount field.\n"
@@ -4368,8 +4396,7 @@ static RPCHelpMan walletcreatefundedpsbt()
                             },
                             {"replaceable", RPCArg::Type::BOOL, /* default */ "wallet default", "Marks this transaction as BIP125 replaceable.\n"
                                                           "Allows this transaction to be replaced by a transaction with higher fees"},
-                            {"conf_target", RPCArg::Type::NUM, /* default */ "wallet -txconfirmtarget", "Confirmation target (in blocks)\n"
-                                                          "or fee rate (for " + CURRENCY_UNIT + "/kB and " + CURRENCY_ATOM + "/B estimate modes)"},
+                            {"conf_target", RPCArg::Type::NUM, /* default */ "wallet -txconfirmtarget", "Confirmation target in blocks"},
                             {"estimate_mode", RPCArg::Type::STR, /* default */ "unset", std::string() + "The fee estimate mode, must be one of (case insensitive):\n"
                             "         \"" + FeeModes("\"\n\"") + "\""},
                         },
@@ -4416,7 +4443,7 @@ static RPCHelpMan walletcreatefundedpsbt()
     // Automatically select coins, unless at least one is manually selected. Can
     // be overridden by options.add_inputs.
     coin_control.m_add_inputs = rawTx.vin.size() == 0;
-    FundTransaction(pwallet, rawTx, fee, change_position, request.params[3], coin_control);
+    FundTransaction(pwallet, rawTx, fee, change_position, request.params[3], coin_control, /* override_min_fee */ true);
 
     // Make a blank psbt
     PartiallySignedTransaction psbtx(rawTx);
@@ -4549,9 +4576,9 @@ static const CRPCCommand commands[] =
     { "wallet",             "lockunspent",                      &lockunspent,                   {"unlock","transactions"} },
     { "wallet",             "removeprunedfunds",                &removeprunedfunds,             {"txid"} },
     { "wallet",             "rescanblockchain",                 &rescanblockchain,              {"start_height", "stop_height"} },
-    { "wallet",             "send",                             &send,                          {"outputs","conf_target","estimate_mode","options"} },
-    { "wallet",             "sendmany",                         &sendmany,                      {"dummy","amounts","minconf","comment","subtractfeefrom","replaceable","conf_target","estimate_mode","verbose"} },
-    { "wallet",             "sendtoaddress",                    &sendtoaddress,                 {"address","amount","comment","comment_to","subtractfeefromamount","replaceable","conf_target","estimate_mode","avoid_reuse","verbose"} },
+    { "wallet",             "send",                             &send,                          {"outputs","conf_target","estimate_mode","fee_rate","options"} },
+    { "wallet",             "sendmany",                         &sendmany,                      {"dummy","amounts","minconf","comment","subtractfeefrom","replaceable","conf_target","estimate_mode","fee_rate","verbose"} },
+    { "wallet",             "sendtoaddress",                    &sendtoaddress,                 {"address","amount","comment","comment_to","subtractfeefromamount","replaceable","conf_target","estimate_mode","avoid_reuse","fee_rate","verbose"} },
     { "wallet",             "sethdseed",                        &sethdseed,                     {"newkeypool","seed"} },
     { "wallet",             "setlabel",                         &setlabel,                      {"address","label"} },
     { "wallet",             "settxfee",                         &settxfee,                      {"amount"} },
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
index 3ce8272fb9..ff8bfff872 100644
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -2818,7 +2818,7 @@ bool CWallet::CreateTransactionInternal(
             // Do not, ever, assume that it's fine to change the fee rate if the user has explicitly
             // provided one
             if (coin_control.m_feerate && nFeeRateNeeded > *coin_control.m_feerate) {
-                error = strprintf(_("Fee rate (%s) is lower than the minimum fee rate setting (%s)"), coin_control.m_feerate->ToString(), nFeeRateNeeded.ToString());
+                error = strprintf(_("Fee rate (%s) is lower than the minimum fee rate setting (%s)"), coin_control.m_feerate->ToString(FeeEstimateMode::SAT_VB), nFeeRateNeeded.ToString(FeeEstimateMode::SAT_VB));
                 return false;
             }
 
diff --git a/test/functional/rpc_estimatefee.py b/test/functional/rpc_estimatefee.py
index 1fff9e1512..3b76c7dd1e 100755
--- a/test/functional/rpc_estimatefee.py
+++ b/test/functional/rpc_estimatefee.py
@@ -28,7 +28,7 @@ class EstimateFeeTest(BitcoinTestFramework):
 
         # wrong type for estimatesmartfee(estimate_mode)
         assert_raises_rpc_error(-3, "Expected type string, got number", self.nodes[0].estimatesmartfee, 1, 1)
-        assert_raises_rpc_error(-8, "Invalid estimate_mode parameter", self.nodes[0].estimatesmartfee, 1, 'foo')
+        assert_raises_rpc_error(-8, 'Invalid estimate_mode parameter, must be one of: "unset", "economical", "conservative"', self.nodes[0].estimatesmartfee, 1, 'foo')
 
         # wrong type for estimaterawfee(threshold)
         assert_raises_rpc_error(-3, "Expected type number, got string", self.nodes[0].estimaterawfee, 1, 'foo')
diff --git a/test/functional/rpc_fundrawtransaction.py b/test/functional/rpc_fundrawtransaction.py
index 503993162b..f987867e61 100755
--- a/test/functional/rpc_fundrawtransaction.py
+++ b/test/functional/rpc_fundrawtransaction.py
@@ -90,7 +90,6 @@ class RawTransactionsTest(BitcoinTestFramework):
         self.test_op_return()
         self.test_watchonly()
         self.test_all_watched_funds()
-        self.test_feerate_with_conf_target_and_estimate_mode()
         self.test_option_feerate()
         self.test_address_reuse()
         self.test_option_subtract_fee_from_outputs()
@@ -708,74 +707,86 @@ class RawTransactionsTest(BitcoinTestFramework):
         wwatch.unloadwallet()
 
     def test_option_feerate(self):
-        self.log.info("Test fundrawtxn feeRate option")
-
-        # Make sure there is exactly one input so coin selection can't skew the result.
-        assert_equal(len(self.nodes[3].listunspent(1)), 1)
-
-        inputs = []
-        outputs = {self.nodes[3].getnewaddress() : 1}
-        rawtx = self.nodes[3].createrawtransaction(inputs, outputs)
-        result = self.nodes[3].fundrawtransaction(rawtx)  # uses self.min_relay_tx_fee (set by settxfee)
-        result2 = self.nodes[3].fundrawtransaction(rawtx, {"feeRate": 2 * self.min_relay_tx_fee})
-        result3 = self.nodes[3].fundrawtransaction(rawtx, {"feeRate": 10 * self.min_relay_tx_fee})
-        assert_raises_rpc_error(-4, "Fee exceeds maximum configured by user (e.g. -maxtxfee, maxfeerate)", self.nodes[3].fundrawtransaction, rawtx, {"feeRate": 1})
-        result_fee_rate = result['fee'] * 1000 / count_bytes(result['hex'])
-        assert_fee_amount(result2['fee'], count_bytes(result2['hex']), 2 * result_fee_rate)
-        assert_fee_amount(result3['fee'], count_bytes(result3['hex']), 10 * result_fee_rate)
-
-    def test_feerate_with_conf_target_and_estimate_mode(self):
-        self.log.info("Test fundrawtxn passing an explicit fee rate using conf_target and estimate_mode")
+        self.log.info("Test fundrawtxn with explicit fee rates (fee_rate sat/vB and feeRate BTC/kvB)")
         node = self.nodes[3]
         # Make sure there is exactly one input so coin selection can't skew the result.
-        assert_equal(len(node.listunspent(1)), 1)
+        assert_equal(len(self.nodes[3].listunspent(1)), 1)
         inputs = []
         outputs = {node.getnewaddress() : 1}
         rawtx = node.createrawtransaction(inputs, outputs)
 
-        for unit, fee_rate in {"btc/kb": 0.1, "sat/b": 10000}.items():
-            self.log.info("Test fundrawtxn with conf_target {} estimate_mode {} produces expected fee".format(fee_rate, unit))
-            # With no arguments passed, expect fee of 141 sats/b.
-            assert_approx(node.fundrawtransaction(rawtx)["fee"], vexp=0.00000141, vspan=0.00000001)
-            # Expect fee to be 10,000x higher when explicit fee 10,000x greater is specified.
-            result = node.fundrawtransaction(rawtx, {"conf_target": fee_rate, "estimate_mode": unit})
-            assert_approx(result["fee"], vexp=0.0141, vspan=0.0001)
+        result = node.fundrawtransaction(rawtx)  # uses self.min_relay_tx_fee (set by settxfee)
+        btc_kvb_to_sat_vb = 100000  # (1e5)
+        result1 = node.fundrawtransaction(rawtx, {"fee_rate": 2 * btc_kvb_to_sat_vb * self.min_relay_tx_fee})
+        result2 = node.fundrawtransaction(rawtx, {"feeRate": 2 * self.min_relay_tx_fee})
+        result3 = node.fundrawtransaction(rawtx, {"fee_rate": 10 * btc_kvb_to_sat_vb * self.min_relay_tx_fee})
+        result4 = node.fundrawtransaction(rawtx, {"feeRate": 10 * self.min_relay_tx_fee})
+        result_fee_rate = result['fee'] * 1000 / count_bytes(result['hex'])
+        assert_fee_amount(result1['fee'], count_bytes(result2['hex']), 2 * result_fee_rate)
+        assert_fee_amount(result2['fee'], count_bytes(result2['hex']), 2 * result_fee_rate)
+        assert_fee_amount(result3['fee'], count_bytes(result3['hex']), 10 * result_fee_rate)
+        assert_fee_amount(result4['fee'], count_bytes(result3['hex']), 10 * result_fee_rate)
 
-        for field, fee_rate in {"conf_target": 0.1, "estimate_mode": "sat/b"}.items():
-            self.log.info("Test fundrawtxn raises RPC error if both feeRate and {} are passed".format(field))
-            assert_raises_rpc_error(
-                -8, "Cannot specify both {} and feeRate".format(field),
-                lambda: node.fundrawtransaction(rawtx, {"feeRate": 0.1, field: fee_rate}))
+        # With no arguments passed, expect fee of 141 satoshis.
+        assert_approx(node.fundrawtransaction(rawtx)["fee"], vexp=0.00000141, vspan=0.00000001)
+        # Expect fee to be 10,000x higher when an explicit fee rate 10,000x greater is specified.
+        result = node.fundrawtransaction(rawtx, {"fee_rate": 10000})
+        assert_approx(result["fee"], vexp=0.0141, vspan=0.0001)
 
         self.log.info("Test fundrawtxn with invalid estimate_mode settings")
         for k, v in {"number": 42, "object": {"foo": "bar"}}.items():
             assert_raises_rpc_error(-3, "Expected type string for estimate_mode, got {}".format(k),
-                lambda: self.nodes[1].fundrawtransaction(rawtx, {"estimate_mode": v, "conf_target": 0.1}))
-        for mode in ["foo", Decimal("3.141592")]:
-            assert_raises_rpc_error(-8, "Invalid estimate_mode parameter",
-                lambda: self.nodes[1].fundrawtransaction(rawtx, {"estimate_mode": mode, "conf_target": 0.1}))
+                node.fundrawtransaction, rawtx, {"estimate_mode": v, "conf_target": 0.1, "add_inputs": True})
+        for mode in ["", "foo", Decimal("3.141592")]:
+            assert_raises_rpc_error(-8, 'Invalid estimate_mode parameter, must be one of: "unset", "economical", "conservative"',
+                node.fundrawtransaction, rawtx, {"estimate_mode": mode, "conf_target": 0.1, "add_inputs": True})
 
         self.log.info("Test fundrawtxn with invalid conf_target settings")
-        for mode in ["unset", "economical", "conservative", "btc/kb", "sat/b"]:
+        for mode in ["unset", "economical", "conservative"]:
             self.log.debug("{}".format(mode))
             for k, v in {"string": "", "object": {"foo": "bar"}}.items():
                 assert_raises_rpc_error(-3, "Expected type number for conf_target, got {}".format(k),
-                    lambda: self.nodes[1].fundrawtransaction(rawtx, {"estimate_mode": mode, "conf_target": v}))
-            if mode in ["btc/kb", "sat/b"]:
-                assert_raises_rpc_error(-3, "Amount out of range",
-                    lambda: self.nodes[1].fundrawtransaction(rawtx, {"estimate_mode": mode, "conf_target": -1}))
-                assert_raises_rpc_error(-4, "Fee rate (0.00000000 BTC/kB) is lower than the minimum fee rate setting (0.00001000 BTC/kB)",
-                    lambda: self.nodes[1].fundrawtransaction(rawtx, {"estimate_mode": mode, "conf_target": 0}))
-            else:
-                for n in [-1, 0, 1009]:
-                    assert_raises_rpc_error(-8, "Invalid conf_target, must be between 1 and 1008",
-                        lambda: self.nodes[1].fundrawtransaction(rawtx, {"estimate_mode": mode, "conf_target": n}))
-
-        for unit, fee_rate in {"sat/B": 0.99999999, "BTC/kB": 0.00000999}.items():
-            self.log.info("- raises RPC error 'fee rate too low' if conf_target {} and estimate_mode {} are passed".format(fee_rate, unit))
-            assert_raises_rpc_error(-4, "Fee rate (0.00000999 BTC/kB) is lower than the minimum fee rate setting (0.00001000 BTC/kB)",
-                lambda: self.nodes[1].fundrawtransaction(rawtx, {"estimate_mode": unit, "conf_target": fee_rate, "add_inputs": True}))
-
+                    node.fundrawtransaction, rawtx, {"estimate_mode": mode, "conf_target": v, "add_inputs": True})
+            for n in [-1, 0, 1009]:
+                assert_raises_rpc_error(-8, "Invalid conf_target, must be between 1 and 1008",  # max value of 1008 per src/policy/fees.h
+                    node.fundrawtransaction, rawtx, {"estimate_mode": mode, "conf_target": n, "add_inputs": True})
+
+        self.log.info("Test invalid fee rate settings")
+        assert_raises_rpc_error(-8, "Invalid fee_rate 0.000 sat/vB (must be greater than 0)",
+            node.fundrawtransaction, rawtx, {"fee_rate": 0, "add_inputs": True})
+        assert_raises_rpc_error(-8, "Invalid feeRate 0.00000000 BTC/kvB (must be greater than 0)",
+            node.fundrawtransaction, rawtx, {"feeRate": 0, "add_inputs": True})
+        for param, value in {("fee_rate", 100000), ("feeRate", 1.000)}:
+            assert_raises_rpc_error(-4, "Fee exceeds maximum configured by user (e.g. -maxtxfee, maxfeerate)",
+                node.fundrawtransaction, rawtx, {param: value, "add_inputs": True})
+            assert_raises_rpc_error(-3, "Amount out of range",
+                node.fundrawtransaction, rawtx, {"fee_rate": -1, "add_inputs": True})
+            assert_raises_rpc_error(-3, "Amount is not a number or string",
+                node.fundrawtransaction, rawtx, {"fee_rate": {"foo": "bar"}, "add_inputs": True})
+            assert_raises_rpc_error(-3, "Invalid amount",
+                node.fundrawtransaction, rawtx, {"fee_rate": "", "add_inputs": True})
+
+        self.log.info("Test min fee rate checks are bypassed with fundrawtxn, e.g. a fee_rate under 1 sat/vB is allowed")
+        node.fundrawtransaction(rawtx, {"fee_rate": 0.99999999, "add_inputs": True})
+        node.fundrawtransaction(rawtx, {"feeRate": 0.00000999, "add_inputs": True})
+
+        self.log.info("- raises RPC error if both feeRate and fee_rate are passed")
+        assert_raises_rpc_error(-8, "Cannot specify both fee_rate (sat/vB) and feeRate (BTC/kvB)",
+            node.fundrawtransaction, rawtx, {"fee_rate": 0.1, "feeRate": 0.1, "add_inputs": True})
+
+        self.log.info("- raises RPC error if both feeRate and estimate_mode passed")
+        assert_raises_rpc_error(-8, "Cannot specify both estimate_mode and feeRate",
+            node.fundrawtransaction, rawtx, {"estimate_mode": "economical", "feeRate": 0.1, "add_inputs": True})
+
+        for param in ["feeRate", "fee_rate"]:
+            self.log.info("- raises RPC error if both {} and conf_target are passed".format(param))
+            assert_raises_rpc_error(-8, "Cannot specify both conf_target and {}. Please provide either a confirmation "
+                "target in blocks for automatic fee estimation, or an explicit fee rate.".format(param),
+                node.fundrawtransaction, rawtx, {param: 1, "conf_target": 1, "add_inputs": True})
+
+        self.log.info("- raises RPC error if both fee_rate and estimate_mode are passed")
+        assert_raises_rpc_error(-8, "Cannot specify both estimate_mode and fee_rate",
+            node.fundrawtransaction, rawtx, {"fee_rate": 1, "estimate_mode": "economical", "add_inputs": True})
 
     def test_address_reuse(self):
         """Test no address reuse occurs."""
@@ -803,12 +814,32 @@ class RawTransactionsTest(BitcoinTestFramework):
         outputs = {self.nodes[2].getnewaddress(): 1}
         rawtx = self.nodes[3].createrawtransaction(inputs, outputs)
 
+        # Test subtract fee from outputs with feeRate (BTC/kvB)
         result = [self.nodes[3].fundrawtransaction(rawtx),  # uses self.min_relay_tx_fee (set by settxfee)
             self.nodes[3].fundrawtransaction(rawtx, {"subtractFeeFromOutputs": []}),  # empty subtraction list
             self.nodes[3].fundrawtransaction(rawtx, {"subtractFeeFromOutputs": [0]}),  # uses self.min_relay_tx_fee (set by settxfee)
             self.nodes[3].fundrawtransaction(rawtx, {"feeRate": 2 * self.min_relay_tx_fee}),
             self.nodes[3].fundrawtransaction(rawtx, {"feeRate": 2 * self.min_relay_tx_fee, "subtractFeeFromOutputs": [0]}),]
+        dec_tx = [self.nodes[3].decoderawtransaction(tx_['hex']) for tx_ in result]
+        output = [d['vout'][1 - r['changepos']]['value'] for d, r in zip(dec_tx, result)]
+        change = [d['vout'][r['changepos']]['value'] for d, r in zip(dec_tx, result)]
+
+        assert_equal(result[0]['fee'], result[1]['fee'], result[2]['fee'])
+        assert_equal(result[3]['fee'], result[4]['fee'])
+        assert_equal(change[0], change[1])
+        assert_equal(output[0], output[1])
+        assert_equal(output[0], output[2] + result[2]['fee'])
+        assert_equal(change[0] + result[0]['fee'], change[2])
+        assert_equal(output[3], output[4] + result[4]['fee'])
+        assert_equal(change[3] + result[3]['fee'], change[4])
 
+        # Test subtract fee from outputs with fee_rate (sat/vB)
+        btc_kvb_to_sat_vb = 100000  # (1e5)
+        result = [self.nodes[3].fundrawtransaction(rawtx),  # uses self.min_relay_tx_fee (set by settxfee)
+            self.nodes[3].fundrawtransaction(rawtx, {"subtractFeeFromOutputs": []}),  # empty subtraction list
+            self.nodes[3].fundrawtransaction(rawtx, {"subtractFeeFromOutputs": [0]}),  # uses self.min_relay_tx_fee (set by settxfee)
+            self.nodes[3].fundrawtransaction(rawtx, {"fee_rate": 2 * btc_kvb_to_sat_vb * self.min_relay_tx_fee}),
+            self.nodes[3].fundrawtransaction(rawtx, {"fee_rate": 2 * btc_kvb_to_sat_vb * self.min_relay_tx_fee, "subtractFeeFromOutputs": [0]}),]
         dec_tx = [self.nodes[3].decoderawtransaction(tx_['hex']) for tx_ in result]
         output = [d['vout'][1 - r['changepos']]['value'] for d, r in zip(dec_tx, result)]
         change = [d['vout'][r['changepos']]['value'] for d, r in zip(dec_tx, result)]
diff --git a/test/functional/rpc_psbt.py b/test/functional/rpc_psbt.py
index ca75bcb9bb..498197b5e5 100755
--- a/test/functional/rpc_psbt.py
+++ b/test/functional/rpc_psbt.py
@@ -187,60 +187,74 @@ class PSBTTest(BitcoinTestFramework):
         assert_equal(walletprocesspsbt_out['complete'], True)
         self.nodes[1].sendrawtransaction(self.nodes[1].finalizepsbt(walletprocesspsbt_out['psbt'])['hex'])
 
-        self.log.info("Test walletcreatefundedpsbt feeRate of 0.1 BTC/kB produces a total fee at or slightly below -maxtxfee (~0.05290000)")
-        res = self.nodes[1].walletcreatefundedpsbt(inputs, outputs, 0, {"feeRate": 0.1, "add_inputs": True})
-        assert_approx(res["fee"], 0.055, 0.005)
-
-        self.log.info("Test walletcreatefundedpsbt explicit fee rate with conf_target and estimate_mode")
-        for unit, fee_rate in {"btc/kb": 0.1, "sat/b": 10000}.items():
-            fee = self.nodes[1].walletcreatefundedpsbt(inputs, outputs, 0, {"conf_target": fee_rate, "estimate_mode": unit, "add_inputs": True})["fee"]
-            self.log.info("- conf_target {}, estimate_mode {} produces fee {} at or slightly below -maxtxfee (~0.05290000)".format(fee_rate, unit, fee))
-            assert_approx(fee, vexp=0.055, vspan=0.005)
-
-        for field, fee_rate in {"conf_target": 0.1, "estimate_mode": "sat/b"}.items():
-            self.log.info("- raises RPC error if both feeRate and {} are passed".format(field))
-            assert_raises_rpc_error(-8, "Cannot specify both {} and feeRate".format(field),
-                lambda: self.nodes[1].walletcreatefundedpsbt(inputs, outputs, 0, {"feeRate": 0.1, field: fee_rate, "add_inputs": True}))
+        self.log.info("Test walletcreatefundedpsbt fee rate of 10000 sat/vB and 0.1 BTC/kvB produces a total fee at or slightly below -maxtxfee (~0.05290000)")
+        res1 = self.nodes[1].walletcreatefundedpsbt(inputs, outputs, 0, {"fee_rate": 10000, "add_inputs": True})
+        assert_approx(res1["fee"], 0.055, 0.005)
+        res2 = self.nodes[1].walletcreatefundedpsbt(inputs, outputs, 0, {"feeRate": 0.1, "add_inputs": True})
+        assert_approx(res2["fee"], 0.055, 0.005)
+        self.log.info("Test min fee rate checks with walletcreatefundedpsbt are bypassed, e.g. a fee_rate under 1 sat/vB is allowed")
+        res3 = self.nodes[1].walletcreatefundedpsbt(inputs, outputs, 0, {"fee_rate": 0.99999999, "add_inputs": True})
+        assert_approx(res3["fee"], 0.00000381, 0.0000001)
+        res4 = self.nodes[1].walletcreatefundedpsbt(inputs, outputs, 0, {"feeRate": 0.00000999, "add_inputs": True})
+        assert_approx(res4["fee"], 0.00000381, 0.0000001)
+
+        self.log.info("Test invalid fee rate settings")
+        assert_raises_rpc_error(-8, "Invalid fee_rate 0.000 sat/vB (must be greater than 0)",
+            self.nodes[1].walletcreatefundedpsbt, inputs, outputs, 0, {"fee_rate": 0, "add_inputs": True})
+        assert_raises_rpc_error(-8, "Invalid feeRate 0.00000000 BTC/kvB (must be greater than 0)",
+            self.nodes[1].walletcreatefundedpsbt, inputs, outputs, 0, {"feeRate": 0, "add_inputs": True})
+        for param, value in {("fee_rate", 100000), ("feeRate", 1)}:
+            assert_raises_rpc_error(-4, "Fee exceeds maximum configured by user (e.g. -maxtxfee, maxfeerate)",
+                self.nodes[1].walletcreatefundedpsbt, inputs, outputs, 0, {param: value, "add_inputs": True})
+            assert_raises_rpc_error(-3, "Amount out of range",
+                self.nodes[1].walletcreatefundedpsbt, inputs, outputs, 0, {"fee_rate": -1, "add_inputs": True})
+            assert_raises_rpc_error(-3, "Amount is not a number or string",
+                self.nodes[1].walletcreatefundedpsbt, inputs, outputs, 0, {"fee_rate": {"foo": "bar"}, "add_inputs": True})
+            assert_raises_rpc_error(-3, "Invalid amount",
+                self.nodes[1].walletcreatefundedpsbt, inputs, outputs, 0, {"fee_rate": "", "add_inputs": True})
+
+        self.log.info("- raises RPC error if both feeRate and fee_rate are passed")
+        assert_raises_rpc_error(-8, "Cannot specify both fee_rate (sat/vB) and feeRate (BTC/kvB)",
+            self.nodes[1].walletcreatefundedpsbt, inputs, outputs, 0, {"fee_rate": 0.1, "feeRate": 0.1, "add_inputs": True})
+
+        self.log.info("- raises RPC error if both feeRate and estimate_mode passed")
+        assert_raises_rpc_error(-8, "Cannot specify both estimate_mode and feeRate",
+            self.nodes[1].walletcreatefundedpsbt, inputs, outputs, 0, {"estimate_mode": "economical", "feeRate": 0.1, "add_inputs": True})
+
+        for param in ["feeRate", "fee_rate"]:
+            self.log.info("- raises RPC error if both {} and conf_target are passed".format(param))
+            assert_raises_rpc_error(-8, "Cannot specify both conf_target and {}. Please provide either a confirmation "
+                "target in blocks for automatic fee estimation, or an explicit fee rate.".format(param),
+                self.nodes[1].walletcreatefundedpsbt ,inputs, outputs, 0, {param: 1, "conf_target": 1, "add_inputs": True})
+
+        self.log.info("- raises RPC error if both fee_rate and estimate_mode are passed")
+        assert_raises_rpc_error(-8, "Cannot specify both estimate_mode and fee_rate",
+            self.nodes[1].walletcreatefundedpsbt ,inputs, outputs, 0, {"fee_rate": 1, "estimate_mode": "economical", "add_inputs": True})
 
         self.log.info("- raises RPC error with invalid estimate_mode settings")
         for k, v in {"number": 42, "object": {"foo": "bar"}}.items():
             assert_raises_rpc_error(-3, "Expected type string for estimate_mode, got {}".format(k),
-                lambda: self.nodes[1].walletcreatefundedpsbt(inputs, outputs, 0, {"estimate_mode": v, "conf_target": 0.1, "add_inputs": True}))
-        for mode in ["foo", Decimal("3.141592")]:
-            assert_raises_rpc_error(-8, "Invalid estimate_mode parameter",
-                lambda: self.nodes[1].walletcreatefundedpsbt(inputs, outputs, 0, {"estimate_mode": mode, "conf_target": 0.1, "add_inputs": True}))
-
-        self.log.info("- raises RPC error if estimate_mode is passed without a conf_target")
-        for unit in ["SAT/B", "BTC/KB"]:
-            assert_raises_rpc_error(-8, "Selected estimate_mode {} requires a fee rate to be specified in conf_target".format(unit),
-                lambda: self.nodes[1].walletcreatefundedpsbt(inputs, outputs, 0, {"estimate_mode": unit}))
+                self.nodes[1].walletcreatefundedpsbt, inputs, outputs, 0, {"estimate_mode": v, "conf_target": 0.1, "add_inputs": True})
+        for mode in ["", "foo", Decimal("3.141592")]:
+            assert_raises_rpc_error(-8, 'Invalid estimate_mode parameter, must be one of: "unset", "economical", "conservative"',
+                self.nodes[1].walletcreatefundedpsbt, inputs, outputs, 0, {"estimate_mode": mode, "conf_target": 0.1, "add_inputs": True})
 
         self.log.info("- raises RPC error with invalid conf_target settings")
-        for mode in ["unset", "economical", "conservative", "btc/kb", "sat/b"]:
+        for mode in ["unset", "economical", "conservative"]:
             self.log.debug("{}".format(mode))
             for k, v in {"string": "", "object": {"foo": "bar"}}.items():
                 assert_raises_rpc_error(-3, "Expected type number for conf_target, got {}".format(k),
-                    lambda: self.nodes[1].walletcreatefundedpsbt(inputs, outputs, 0, {"estimate_mode": mode, "conf_target": v, "add_inputs": True}))
-            if mode in ["btc/kb", "sat/b"]:
-                assert_raises_rpc_error(-3, "Amount out of range",
-                    lambda: self.nodes[1].walletcreatefundedpsbt(inputs, outputs, 0, {"estimate_mode": mode, "conf_target": -1, "add_inputs": True}))
-                assert_raises_rpc_error(-4, "Fee rate (0.00000000 BTC/kB) is lower than the minimum fee rate setting (0.00001000 BTC/kB)",
-                    lambda: self.nodes[1].walletcreatefundedpsbt(inputs, outputs, 0, {"estimate_mode": mode, "conf_target": 0, "add_inputs": True}))
-            else:
-                for n in [-1, 0, 1009]:
-                    assert_raises_rpc_error(-8, "Invalid conf_target, must be between 1 and 1008",
-                        lambda: self.nodes[1].walletcreatefundedpsbt(inputs, outputs, 0, {"estimate_mode": mode, "conf_target": n, "add_inputs": True}))
-
-        for unit, fee_rate in {"SAT/B": 0.99999999, "BTC/KB": 0.00000999}.items():
-            self.log.info("- raises RPC error 'fee rate too low' if conf_target {} and estimate_mode {} are passed".format(fee_rate, unit))
-            assert_raises_rpc_error(-4, "Fee rate (0.00000999 BTC/kB) is lower than the minimum fee rate setting (0.00001000 BTC/kB)",
-                lambda: self.nodes[1].walletcreatefundedpsbt(inputs, outputs, 0, {"estimate_mode": unit, "conf_target": fee_rate, "add_inputs": True}))
-
-        self.log.info("Test walletcreatefundedpsbt feeRate of 10 BTC/kB produces total fee well above -maxtxfee and raises RPC error")
+                    self.nodes[1].walletcreatefundedpsbt, inputs, outputs, 0, {"estimate_mode": mode, "conf_target": v, "add_inputs": True})
+            for n in [-1, 0, 1009]:
+                assert_raises_rpc_error(-8, "Invalid conf_target, must be between 1 and 1008",  # max value of 1008 per src/policy/fees.h
+                    self.nodes[1].walletcreatefundedpsbt, inputs, outputs, 0, {"estimate_mode": mode, "conf_target": n, "add_inputs": True})
+
+        self.log.info("Test walletcreatefundedpsbt with too-high fee rate produces total fee well above -maxtxfee and raises RPC error")
         # previously this was silently capped at -maxtxfee
         for bool_add, outputs_array in {True: outputs, False: [{self.nodes[1].getnewaddress(): 1}]}.items():
-            assert_raises_rpc_error(-4, "Fee exceeds maximum configured by user (e.g. -maxtxfee, maxfeerate)",
-                self.nodes[1].walletcreatefundedpsbt, inputs, outputs_array, 0, {"feeRate": 10, "add_inputs": bool_add})
+            msg = "Fee exceeds maximum configured by user (e.g. -maxtxfee, maxfeerate)"
+            assert_raises_rpc_error(-4, msg, self.nodes[1].walletcreatefundedpsbt, inputs, outputs_array, 0, {"fee_rate": 1000000, "add_inputs": bool_add})
+            assert_raises_rpc_error(-4, msg, self.nodes[1].walletcreatefundedpsbt, inputs, outputs_array, 0, {"feeRate": 1, "add_inputs": bool_add})
 
         self.log.info("Test various PSBT operations")
         # partially sign multisig things with node 1
diff --git a/test/functional/wallet_basic.py b/test/functional/wallet_basic.py
index 40daffd2c2..ead56046a4 100755
--- a/test/functional/wallet_basic.py
+++ b/test/functional/wallet_basic.py
@@ -4,6 +4,7 @@
 # file COPYING or http://www.opensource.org/licenses/mit-license.php.
 """Test the wallet."""
 from decimal import Decimal
+from itertools import product
 
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import (
@@ -14,6 +15,8 @@ from test_framework.util import (
 )
 from test_framework.wallet_util import test_address
 
+OUT_OF_RANGE = "Amount out of range"
+
 
 class WalletTest(BitcoinTestFramework):
     def set_test_params(self):
@@ -74,7 +77,7 @@ class WalletTest(BitcoinTestFramework):
         assert_equal(len(self.nodes[1].listunspent()), 1)
         assert_equal(len(self.nodes[2].listunspent()), 0)
 
-        self.log.info("test gettxout")
+        self.log.info("Test gettxout")
         confirmed_txid, confirmed_index = utxos[0]["txid"], utxos[0]["vout"]
         # First, outputs that are unspent both in the chain and in the
         # mempool should appear with or without include_mempool
@@ -87,7 +90,7 @@ class WalletTest(BitcoinTestFramework):
         self.nodes[0].sendtoaddress(self.nodes[2].getnewaddress(), 11)
         mempool_txid = self.nodes[0].sendtoaddress(self.nodes[2].getnewaddress(), 10)
 
-        self.log.info("test gettxout (second part)")
+        self.log.info("Test gettxout (second part)")
         # utxo spent in mempool should be visible if you exclude mempool
         # but invisible if you include mempool
         txout = self.nodes[0].gettxout(confirmed_txid, confirmed_index, False)
@@ -227,65 +230,41 @@ class WalletTest(BitcoinTestFramework):
         assert_equal(self.nodes[2].getbalance(), node_2_bal)
         node_0_bal = self.check_fee_amount(self.nodes[0].getbalance(), node_0_bal + Decimal('10'), fee_per_byte, self.get_vsize(self.nodes[2].gettransaction(txid)['hex']))
 
-        self.log.info("Test case-insensitive explicit fee rate (sendmany as BTC/kB)")
-        # Throw if no conf_target provided
-        assert_raises_rpc_error(-8, "Selected estimate_mode bTc/kB requires a fee rate to be specified in conf_target",
-            self.nodes[2].sendmany,
-            amounts={ address: 10 },
-            estimate_mode='bTc/kB')
-        # Throw if negative feerate
-        assert_raises_rpc_error(-3, "Amount out of range",
-            self.nodes[2].sendmany,
-            amounts={ address: 10 },
-            conf_target=-1,
-            estimate_mode='bTc/kB')
-        fee_per_kb = 0.0002500
-        explicit_fee_per_byte = Decimal(fee_per_kb) / 1000
-        txid = self.nodes[2].sendmany(
-            amounts={ address: 10 },
-            conf_target=fee_per_kb,
-            estimate_mode='bTc/kB',
-        )
-        self.nodes[2].generate(1)
-        self.sync_all(self.nodes[0:3])
-        node_2_bal = self.check_fee_amount(self.nodes[2].getbalance(), node_2_bal - Decimal('10'), explicit_fee_per_byte, self.get_vsize(self.nodes[2].gettransaction(txid)['hex']))
-        assert_equal(self.nodes[2].getbalance(), node_2_bal)
-        node_0_bal += Decimal('10')
-        assert_equal(self.nodes[0].getbalance(), node_0_bal)
+        self.log.info("Test sendmany with fee_rate param (explicit fee rate in sat/vB)")
+        fee_rate_sat_vb = 2
+        fee_rate_btc_kvb = fee_rate_sat_vb * 1e3 / 1e8
+        explicit_fee_rate_btc_kvb = Decimal(fee_rate_btc_kvb) / 1000
 
-        self.log.info("Test case-insensitive explicit fee rate (sendmany as sat/B)")
-        # Throw if no conf_target provided
-        assert_raises_rpc_error(-8, "Selected estimate_mode sat/b requires a fee rate to be specified in conf_target",
-            self.nodes[2].sendmany,
-            amounts={ address: 10 },
-            estimate_mode='sat/b')
-        # Throw if negative feerate
-        assert_raises_rpc_error(-3, "Amount out of range",
-            self.nodes[2].sendmany,
-            amounts={ address: 10 },
-            conf_target=-1,
-            estimate_mode='sat/b')
-        fee_sat_per_b = 2
-        fee_per_kb = fee_sat_per_b / 100000.0
-        explicit_fee_per_byte = Decimal(fee_per_kb) / 1000
-        txid = self.nodes[2].sendmany(
-            amounts={ address: 10 },
-            conf_target=fee_sat_per_b,
-            estimate_mode='sAT/b',
-        )
+        # Passing conf_target 0, estimate_mode "" as placeholder arguments should allow fee_rate to apply.
+        txid = self.nodes[2].sendmany(amounts={address: 10}, conf_target=0, estimate_mode="", fee_rate=fee_rate_sat_vb)
         self.nodes[2].generate(1)
         self.sync_all(self.nodes[0:3])
         balance = self.nodes[2].getbalance()
-        node_2_bal = self.check_fee_amount(balance, node_2_bal - Decimal('10'), explicit_fee_per_byte, self.get_vsize(self.nodes[2].gettransaction(txid)['hex']))
+        node_2_bal = self.check_fee_amount(balance, node_2_bal - Decimal('10'), explicit_fee_rate_btc_kvb, self.get_vsize(self.nodes[2].gettransaction(txid)['hex']))
         assert_equal(balance, node_2_bal)
         node_0_bal += Decimal('10')
         assert_equal(self.nodes[0].getbalance(), node_0_bal)
 
+        for key in ["totalFee", "feeRate"]:
+            assert_raises_rpc_error(-8, "Unknown named parameter key", self.nodes[2].sendtoaddress, address=address, amount=1, fee_rate=1, key=1)
+
         # Test setting explicit fee rate just below the minimum.
-        for unit, fee_rate in {"BTC/kB": 0.00000999, "sat/B": 0.99999999}.items():
-            self.log.info("Test sendmany raises 'fee rate too low' if conf_target {} and estimate_mode {} are passed".format(fee_rate, unit))
-            assert_raises_rpc_error(-6, "Fee rate (0.00000999 BTC/kB) is lower than the minimum fee rate setting (0.00001000 BTC/kB)",
-                self.nodes[2].sendmany, amounts={address: 10}, estimate_mode=unit, conf_target=fee_rate)
+        self.log.info("Test sendmany raises 'fee rate too low' if fee_rate of 0.99999999 is passed")
+        assert_raises_rpc_error(-6, "Fee rate (0.999 sat/vB) is lower than the minimum fee rate setting (1.000 sat/vB)",
+            self.nodes[2].sendmany, amounts={address: 10}, fee_rate=0.99999999)
+
+        self.log.info("Test sendmany raises if fee_rate of 0 or -1 is passed")
+        assert_raises_rpc_error(-6, "Fee rate (0.000 sat/vB) is lower than the minimum fee rate setting (1.000 sat/vB)",
+            self.nodes[2].sendmany, amounts={address: 10}, fee_rate=0)
+        assert_raises_rpc_error(-3, OUT_OF_RANGE, self.nodes[2].sendmany, amounts={address: 10}, fee_rate=-1)
+
+        self.log.info("Test sendmany raises if an invalid conf_target or estimate_mode is passed")
+        for target, mode in product([-1, 0, 1009], ["economical", "conservative"]):
+            assert_raises_rpc_error(-8, "Invalid conf_target, must be between 1 and 1008",  # max value of 1008 per src/policy/fees.h
+                self.nodes[2].sendmany, amounts={address: 1}, conf_target=target, estimate_mode=mode)
+        for target, mode in product([-1, 0], ["btc/kb", "sat/b"]):
+            assert_raises_rpc_error(-8, 'Invalid estimate_mode parameter, must be one of: "unset", "economical", "conservative"',
+                self.nodes[2].sendmany, amounts={address: 1}, conf_target=target, estimate_mode=mode)
 
         self.start_node(3, self.nodes[3].extra_args)
         self.connect_nodes(0, 3)
@@ -318,7 +297,7 @@ class WalletTest(BitcoinTestFramework):
                 assert_equal(uTx['amount'], Decimal('0'))
         assert found
 
-        # do some -walletbroadcast tests
+        self.log.info("Test -walletbroadcast")
         self.stop_nodes()
         self.start_node(0, ["-walletbroadcast=0"])
         self.start_node(1, ["-walletbroadcast=0"])
@@ -378,7 +357,7 @@ class WalletTest(BitcoinTestFramework):
 
         # General checks for errors from incorrect inputs
         # This will raise an exception because the amount is negative
-        assert_raises_rpc_error(-3, "Amount out of range", self.nodes[0].sendtoaddress, self.nodes[2].getnewaddress(), "-1")
+        assert_raises_rpc_error(-3, OUT_OF_RANGE, self.nodes[0].sendtoaddress, self.nodes[2].getnewaddress(), "-1")
 
         # This will raise an exception because the amount type is wrong
         assert_raises_rpc_error(-3, "Invalid amount", self.nodes[0].sendtoaddress, self.nodes[2].getnewaddress(), "1f-4")
@@ -420,78 +399,43 @@ class WalletTest(BitcoinTestFramework):
             self.nodes[0].generate(1)
             self.sync_all(self.nodes[0:3])
 
-            self.log.info("Test case-insensitive explicit fee rate (sendtoaddress as BTC/kB)")
-            self.nodes[0].generate(1)
-            self.sync_all(self.nodes[0:3])
+            self.log.info("Test sendtoaddress with fee_rate param (explicit fee rate in sat/vB)")
             prebalance = self.nodes[2].getbalance()
             assert prebalance > 2
             address = self.nodes[1].getnewaddress()
-            # Throw if no conf_target provided
-            assert_raises_rpc_error(-8, "Selected estimate_mode BTc/Kb requires a fee rate to be specified in conf_target",
-                self.nodes[2].sendtoaddress,
-                address=address,
-                amount=1.0,
-                estimate_mode='BTc/Kb')
-            # Throw if negative feerate
-            assert_raises_rpc_error(-3, "Amount out of range",
-                self.nodes[2].sendtoaddress,
-                address=address,
-                amount=1.0,
-                conf_target=-1,
-                estimate_mode='btc/kb')
-            txid = self.nodes[2].sendtoaddress(
-                address=address,
-                amount=1.0,
-                conf_target=0.00002500,
-                estimate_mode='btc/kb',
-            )
-            tx_size = self.get_vsize(self.nodes[2].gettransaction(txid)['hex'])
-            self.sync_all(self.nodes[0:3])
-            self.nodes[0].generate(1)
-            self.sync_all(self.nodes[0:3])
-            postbalance = self.nodes[2].getbalance()
-            fee = prebalance - postbalance - Decimal('1')
-            assert_fee_amount(fee, tx_size, Decimal('0.00002500'))
+            amount = 3
+            fee_rate_sat_vb = 2
+            fee_rate_btc_kvb = fee_rate_sat_vb * 1e3 / 1e8
 
-            self.sync_all(self.nodes[0:3])
-
-            self.log.info("Test case-insensitive explicit fee rate (sendtoaddress as sat/B)")
-            self.nodes[0].generate(1)
-            prebalance = self.nodes[2].getbalance()
-            assert prebalance > 2
-            address = self.nodes[1].getnewaddress()
-            # Throw if no conf_target provided
-            assert_raises_rpc_error(-8, "Selected estimate_mode SAT/b requires a fee rate to be specified in conf_target",
-                self.nodes[2].sendtoaddress,
-                address=address,
-                amount=1.0,
-                estimate_mode='SAT/b')
-            # Throw if negative feerate
-            assert_raises_rpc_error(-3, "Amount out of range",
-                self.nodes[2].sendtoaddress,
-                address=address,
-                amount=1.0,
-                conf_target=-1,
-                estimate_mode='SAT/b')
-            txid = self.nodes[2].sendtoaddress(
-                address=address,
-                amount=1.0,
-                conf_target=2,
-                estimate_mode='SAT/B',
-            )
+            # Passing conf_target 0, estimate_mode "" as placeholder arguments should allow fee_rate to apply.
+            txid = self.nodes[2].sendtoaddress(address=address, amount=amount, conf_target=0, estimate_mode="", fee_rate=fee_rate_sat_vb)
             tx_size = self.get_vsize(self.nodes[2].gettransaction(txid)['hex'])
-            self.sync_all(self.nodes[0:3])
             self.nodes[0].generate(1)
             self.sync_all(self.nodes[0:3])
             postbalance = self.nodes[2].getbalance()
-            fee = prebalance - postbalance - Decimal('1')
-            assert_fee_amount(fee, tx_size, Decimal('0.00002000'))
+            fee = prebalance - postbalance - Decimal(amount)
+            assert_fee_amount(fee, tx_size, Decimal(fee_rate_btc_kvb))
+
+            for key in ["totalFee", "feeRate"]:
+                assert_raises_rpc_error(-8, "Unknown named parameter key", self.nodes[2].sendtoaddress, address=address, amount=1, fee_rate=1, key=1)
 
             # Test setting explicit fee rate just below the minimum.
-            for unit, fee_rate in {"BTC/kB": 0.00000999, "sat/B": 0.99999999}.items():
-                self.log.info("Test sendtoaddress raises 'fee rate too low' if conf_target {} and estimate_mode {} are passed".format(fee_rate, unit))
-                assert_raises_rpc_error(-6, "Fee rate (0.00000999 BTC/kB) is lower than the minimum fee rate setting (0.00001000 BTC/kB)",
-                    self.nodes[2].sendtoaddress, address=address, amount=1, estimate_mode=unit, conf_target=fee_rate)
+            self.log.info("Test sendtoaddress raises 'fee rate too low' if fee_rate of 0.99999999 is passed")
+            assert_raises_rpc_error(-6, "Fee rate (0.999 sat/vB) is lower than the minimum fee rate setting (1.000 sat/vB)",
+                self.nodes[2].sendtoaddress, address=address, amount=1, fee_rate=0.99999999)
+
+            self.log.info("Test sendtoaddress raises if fee_rate of 0 or -1 is passed")
+            assert_raises_rpc_error(-6, "Fee rate (0.000 sat/vB) is lower than the minimum fee rate setting (1.000 sat/vB)",
+                self.nodes[2].sendtoaddress, address=address, amount=10, fee_rate=0)
+            assert_raises_rpc_error(-3, OUT_OF_RANGE, self.nodes[2].sendtoaddress, address=address, amount=1.0, fee_rate=-1)
+
+            self.log.info("Test sendtoaddress raises if an invalid conf_target or estimate_mode is passed")
+            for target, mode in product([-1, 0, 1009], ["economical", "conservative"]):
+                assert_raises_rpc_error(-8, "Invalid conf_target, must be between 1 and 1008",  # max value of 1008 per src/policy/fees.h
+                    self.nodes[2].sendtoaddress, address=address, amount=1, conf_target=target, estimate_mode=mode)
+            for target, mode in product([-1, 0], ["btc/kb", "sat/b"]):
+                assert_raises_rpc_error(-8, 'Invalid estimate_mode parameter, must be one of: "unset", "economical", "conservative"',
+                    self.nodes[2].sendtoaddress, address=address, amount=1, conf_target=target, estimate_mode=mode)
 
             # 2. Import address from node2 to node1
             self.nodes[1].importaddress(address_to_import)
@@ -549,7 +493,7 @@ class WalletTest(BitcoinTestFramework):
         ]
         chainlimit = 6
         for m in maintenance:
-            self.log.info("check " + m)
+            self.log.info("Test " + m)
             self.stop_nodes()
             # set lower ancestor limit for later
             self.start_node(0, [m, "-limitancestorcount=" + str(chainlimit)])
diff --git a/test/functional/wallet_bumpfee.py b/test/functional/wallet_bumpfee.py
index 88a7778e19..c323aac3cc 100755
--- a/test/functional/wallet_bumpfee.py
+++ b/test/functional/wallet_bumpfee.py
@@ -17,7 +17,7 @@ from decimal import Decimal
 import io
 
 from test_framework.blocktools import add_witness_commitment, create_block, create_coinbase, send_to_witness
-from test_framework.messages import BIP125_SEQUENCE_NUMBER, COIN, CTransaction
+from test_framework.messages import BIP125_SEQUENCE_NUMBER, CTransaction
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import (
     assert_equal,
@@ -29,15 +29,13 @@ from test_framework.util import (
 WALLET_PASSPHRASE = "test"
 WALLET_PASSPHRASE_TIMEOUT = 3600
 
-# Fee rates (in BTC per 1000 vbytes)
-INSUFFICIENT = 0.00001000
-ECONOMICAL   = 0.00050000
-NORMAL       = 0.00100000
-HIGH         = 0.00500000
-TOO_HIGH     = 1.00000000
+# Fee rates (sat/vB)
+INSUFFICIENT =      1
+ECONOMICAL   =     50
+NORMAL       =    100
+HIGH         =    500
+TOO_HIGH     = 100000
 
-BTC_MODE = "BTC/kB"
-SAT_MODE = "sat/B"
 
 class BumpFeeTest(BitcoinTestFramework):
     def set_test_params(self):
@@ -78,7 +76,7 @@ class BumpFeeTest(BitcoinTestFramework):
 
         self.log.info("Running tests")
         dest_address = peer_node.getnewaddress()
-        for mode in ["default", "fee_rate", BTC_MODE, SAT_MODE]:
+        for mode in ["default", "fee_rate"]:
             test_simple_bumpfee_succeeds(self, mode, rbf_node, peer_node, dest_address)
         self.test_invalid_parameters(rbf_node, peer_node, dest_address)
         test_segwit_bumpfee_succeeds(self, rbf_node, dest_address)
@@ -105,50 +103,44 @@ class BumpFeeTest(BitcoinTestFramework):
         self.sync_mempools((rbf_node, peer_node))
         assert rbfid in rbf_node.getrawmempool() and rbfid in peer_node.getrawmempool()
 
-        assert_raises_rpc_error(-3, "Unexpected key totalFee", rbf_node.bumpfee, rbfid, {"totalFee": NORMAL})
-        assert_raises_rpc_error(-4, "is too high (cannot be higher than", rbf_node.bumpfee, rbfid, {"fee_rate": TOO_HIGH})
+        for key in ["totalFee", "feeRate"]:
+            assert_raises_rpc_error(-3, "Unexpected key {}".format(key), rbf_node.bumpfee, rbfid, {key: NORMAL})
 
-        # For each fee mode, bumping to just above minrelay should fail to increase the total fee enough.
-        for options in [{"fee_rate": INSUFFICIENT}, {"conf_target": INSUFFICIENT, "estimate_mode": BTC_MODE}, {"conf_target": 1, "estimate_mode": SAT_MODE}]:
-            assert_raises_rpc_error(-8, "Insufficient total fee", rbf_node.bumpfee, rbfid, options)
+        # Bumping to just above minrelay should fail to increase the total fee enough.
+        assert_raises_rpc_error(-8, "Insufficient total fee 0.00000141, must be at least 0.00001704 (oldFee 0.00000999 + incrementalFee 0.00000705)",
+            rbf_node.bumpfee, rbfid, {"fee_rate": INSUFFICIENT})
 
-        self.log.info("Test explicit fee rate raises RPC error if estimate_mode is passed without a conf_target")
-        for unit, fee_rate in {"SAT/B": 100, "BTC/KB": NORMAL}.items():
-            assert_raises_rpc_error(-8, "Selected estimate_mode {} requires a fee rate to be specified in conf_target".format(unit),
-                                    rbf_node.bumpfee, rbfid, {"fee_rate": fee_rate, "estimate_mode": unit})
+        self.log.info("Test invalid fee rate settings")
+        assert_raises_rpc_error(-8, "Insufficient total fee 0.00, must be at least 0.00001704 (oldFee 0.00000999 + incrementalFee 0.00000705)",
+            rbf_node.bumpfee, rbfid, {"fee_rate": 0})
+        assert_raises_rpc_error(-4, "Specified or calculated fee 0.141 is too high (cannot be higher than -maxtxfee 0.10",
+            rbf_node.bumpfee, rbfid, {"fee_rate": TOO_HIGH})
+        assert_raises_rpc_error(-3, "Amount out of range", rbf_node.bumpfee, rbfid, {"fee_rate": -1})
+        for value in [{"foo": "bar"}, True]:
+            assert_raises_rpc_error(-3, "Amount is not a number or string", rbf_node.bumpfee, rbfid, {"fee_rate": value})
+        assert_raises_rpc_error(-3, "Invalid amount", rbf_node.bumpfee, rbfid, {"fee_rate": ""})
 
         self.log.info("Test explicit fee rate raises RPC error if both fee_rate and conf_target are passed")
-        error_both = "Cannot specify both conf_target and fee_rate. Please provide either a confirmation " \
-                     "target in blocks for automatic fee estimation, or an explicit fee rate."
-        assert_raises_rpc_error(-8, error_both, rbf_node.bumpfee, rbfid, {"conf_target": NORMAL, "fee_rate": NORMAL})
+        assert_raises_rpc_error(-8, "Cannot specify both conf_target and fee_rate. Please provide either a confirmation "
+            "target in blocks for automatic fee estimation, or an explicit fee rate.",
+            rbf_node.bumpfee, rbfid, {"conf_target": NORMAL, "fee_rate": NORMAL})
+
+        self.log.info("Test explicit fee rate raises RPC error if both fee_rate and estimate_mode are passed")
+        assert_raises_rpc_error(-8, "Cannot specify both estimate_mode and fee_rate",
+            rbf_node.bumpfee, rbfid, {"estimate_mode": "economical", "fee_rate": NORMAL})
 
         self.log.info("Test invalid conf_target settings")
         assert_raises_rpc_error(-8, "confTarget and conf_target options should not both be set",
-                                rbf_node.bumpfee, rbfid, {"confTarget": 123, "conf_target": 456})
-        for field in ["confTarget", "conf_target"]:
-            assert_raises_rpc_error(-4, "is too high (cannot be higher than -maxtxfee",
-                                    lambda: rbf_node.bumpfee(rbfid, {"estimate_mode": BTC_MODE, "conf_target": 2009}))
-            assert_raises_rpc_error(-4, "is too high (cannot be higher than -maxtxfee",
-                                    lambda: rbf_node.bumpfee(rbfid, {"estimate_mode": SAT_MODE, "conf_target": 2009 * 10000}))
+            rbf_node.bumpfee, rbfid, {"confTarget": 123, "conf_target": 456})
 
         self.log.info("Test invalid estimate_mode settings")
         for k, v in {"number": 42, "object": {"foo": "bar"}}.items():
             assert_raises_rpc_error(-3, "Expected type string for estimate_mode, got {}".format(k),
-                                    lambda: rbf_node.bumpfee(rbfid, {"estimate_mode": v, "fee_rate": NORMAL}))
-        for mode in ["foo", Decimal("3.141592")]:
-            assert_raises_rpc_error(-8, "Invalid estimate_mode parameter",
-                                    lambda: rbf_node.bumpfee(rbfid, {"estimate_mode": mode, "fee_rate": NORMAL}))
-
-        self.log.info("Test invalid fee_rate settings")
-        for mode in ["unset", "economical", "conservative", BTC_MODE, SAT_MODE]:
-            self.log.debug("{}".format(mode))
-            for k, v in {"string": "", "object": {"foo": "bar"}}.items():
-                assert_raises_rpc_error(-3, "Expected type number for fee_rate, got {}".format(k),
-                                        lambda: rbf_node.bumpfee(rbfid, {"estimate_mode": mode, "fee_rate": v}))
-                assert_raises_rpc_error(-3, "Amount out of range",
-                                        lambda: rbf_node.bumpfee(rbfid, {"estimate_mode": mode, "fee_rate": -1}))
-                assert_raises_rpc_error(-8, "Invalid fee_rate 0.00000000 BTC/kB (must be greater than 0)",
-                                        lambda: rbf_node.bumpfee(rbfid, {"estimate_mode": mode, "fee_rate": 0}))
+                rbf_node.bumpfee, rbfid, {"estimate_mode": v})
+        for mode in ["foo", Decimal("3.1415"), "sat/B", "BTC/kB"]:
+            assert_raises_rpc_error(-8, 'Invalid estimate_mode parameter, must be one of: "unset", "economical", "conservative"',
+                rbf_node.bumpfee, rbfid, {"estimate_mode": mode})
+
         self.clear_mempool()
 
 
@@ -161,13 +153,6 @@ def test_simple_bumpfee_succeeds(self, mode, rbf_node, peer_node, dest_address):
     if mode == "fee_rate":
         bumped_psbt = rbf_node.psbtbumpfee(rbfid, {"fee_rate": NORMAL})
         bumped_tx = rbf_node.bumpfee(rbfid, {"fee_rate": NORMAL})
-    elif mode == BTC_MODE:
-        bumped_psbt = rbf_node.psbtbumpfee(rbfid, {"conf_target": NORMAL, "estimate_mode": BTC_MODE})
-        bumped_tx = rbf_node.bumpfee(rbfid, {"conf_target": NORMAL, "estimate_mode": BTC_MODE})
-    elif mode == SAT_MODE:
-        sat_fee = NORMAL * COIN / 1000  # convert NORMAL from BTC/kB to sat/B
-        bumped_psbt = rbf_node.psbtbumpfee(rbfid, {"conf_target": sat_fee, "estimate_mode": SAT_MODE})
-        bumped_tx = rbf_node.bumpfee(rbfid, {"conf_target": sat_fee, "estimate_mode": SAT_MODE})
     else:
         bumped_psbt = rbf_node.psbtbumpfee(rbfid)
         bumped_tx = rbf_node.bumpfee(rbfid)
@@ -319,11 +304,11 @@ def test_dust_to_fee(self, rbf_node, dest_address):
     # boundary. Thus expected transaction size (p2wpkh, 1 input, 2 outputs) is 140-141 vbytes, usually 141.
     if not 140 <= fulltx["vsize"] <= 141:
         raise AssertionError("Invalid tx vsize of {} (140-141 expected), full tx: {}".format(fulltx["vsize"], fulltx))
-    # Bump with fee_rate of 0.00350250 BTC per 1000 vbytes to create dust.
+    # Bump with fee_rate of 350.25 sat/vB vbytes to create dust.
     # Expected fee is 141 vbytes * fee_rate 0.00350250 BTC / 1000 vbytes = 0.00049385 BTC.
     # or occasionally 140 vbytes * fee_rate 0.00350250 BTC / 1000 vbytes = 0.00049035 BTC.
     # Dust should be dropped to the fee, so actual bump fee is 0.00050000 BTC.
-    bumped_tx = rbf_node.bumpfee(rbfid, {"fee_rate": 0.00350250})
+    bumped_tx = rbf_node.bumpfee(rbfid, {"fee_rate": 350.25})
     full_bumped_tx = rbf_node.getrawtransaction(bumped_tx["txid"], 1)
     assert_equal(bumped_tx["fee"], Decimal("0.00050000"))
     assert_equal(len(fulltx["vout"]), 2)
diff --git a/test/functional/wallet_send.py b/test/functional/wallet_send.py
index 921a726d4b..5da71c85f9 100755
--- a/test/functional/wallet_send.py
+++ b/test/functional/wallet_send.py
@@ -5,13 +5,15 @@
 """Test the send RPC command."""
 
 from decimal import Decimal, getcontext
+from itertools import product
+
 from test_framework.authproxy import JSONRPCException
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import (
     assert_equal,
     assert_fee_amount,
     assert_greater_than,
-    assert_raises_rpc_error
+    assert_raises_rpc_error,
 )
 
 class WalletSendTest(BitcoinTestFramework):
@@ -28,8 +30,8 @@ class WalletSendTest(BitcoinTestFramework):
         self.skip_if_no_wallet()
 
     def test_send(self, from_wallet, to_wallet=None, amount=None, data=None,
-                  arg_conf_target=None, arg_estimate_mode=None,
-                  conf_target=None, estimate_mode=None, add_to_wallet=None, psbt=None,
+                  arg_conf_target=None, arg_estimate_mode=None, arg_fee_rate=None,
+                  conf_target=None, estimate_mode=None, fee_rate=None, add_to_wallet=None, psbt=None,
                   inputs=None, add_inputs=None, change_address=None, change_position=None, change_type=None,
                   include_watching=None, locktime=None, lock_unspents=None, replaceable=None, subtract_fee_from_outputs=None,
                   expect_error=None):
@@ -62,6 +64,8 @@ class WalletSendTest(BitcoinTestFramework):
             options["conf_target"] = conf_target
         if estimate_mode is not None:
             options["estimate_mode"] = estimate_mode
+        if fee_rate is not None:
+            options["fee_rate"] = fee_rate
         if inputs is not None:
             options["inputs"] = inputs
         if add_inputs is not None:
@@ -89,18 +93,19 @@ class WalletSendTest(BitcoinTestFramework):
             options = None
 
         if expect_error is None:
-            res = from_wallet.send(outputs=outputs, conf_target=arg_conf_target, estimate_mode=arg_estimate_mode, options=options)
+            res = from_wallet.send(outputs=outputs, conf_target=arg_conf_target, estimate_mode=arg_estimate_mode, fee_rate=arg_fee_rate, options=options)
         else:
             try:
                 assert_raises_rpc_error(expect_error[0], expect_error[1], from_wallet.send,
-                                        outputs=outputs, conf_target=arg_conf_target, estimate_mode=arg_estimate_mode, options=options)
+                    outputs=outputs, conf_target=arg_conf_target, estimate_mode=arg_estimate_mode, fee_rate=arg_fee_rate, options=options)
             except AssertionError:
                 # Provide debug info if the test fails
                 self.log.error("Unexpected successful result:")
                 self.log.error(arg_conf_target)
                 self.log.error(arg_estimate_mode)
+                self.log.error(arg_fee_rate)
                 self.log.error(options)
-                res = from_wallet.send(outputs=outputs, conf_target=arg_conf_target, estimate_mode=arg_estimate_mode, options=options)
+                res = from_wallet.send(outputs=outputs, conf_target=arg_conf_target, estimate_mode=arg_estimate_mode, fee_rate=arg_fee_rate, options=options)
                 self.log.error(res)
                 if "txid" in res and add_to_wallet:
                     self.log.error("Transaction details:")
@@ -226,10 +231,10 @@ class WalletSendTest(BitcoinTestFramework):
         assert_equal(self.nodes[1].decodepsbt(res1["psbt"])["fee"],
                      self.nodes[1].decodepsbt(res2["psbt"])["fee"])
         # but not at the same time
-        for mode in ["unset", "economical", "conservative", "btc/kb", "sat/b"]:
+        for mode in ["unset", "economical", "conservative"]:
             self.test_send(from_wallet=w0, to_wallet=w1, amount=1, arg_conf_target=1, arg_estimate_mode="economical",
                 conf_target=1, estimate_mode=mode, add_to_wallet=False,
-                expect_error=(-8, "Use either conf_target and estimate_mode or the options dictionary to control fee rate"))
+                expect_error=(-8, "Pass conf_target and estimate_mode either as arguments or in the options object, but not both"))
 
         self.log.info("Create PSBT from watch-only wallet w3, sign with w2...")
         res = self.test_send(from_wallet=w3, to_wallet=w1, amount=1)
@@ -251,60 +256,57 @@ class WalletSendTest(BitcoinTestFramework):
         assert res["complete"]
 
         self.log.info("Test setting explicit fee rate")
-        res1 = self.test_send(from_wallet=w0, to_wallet=w1, amount=1, arg_conf_target=1, arg_estimate_mode="economical", add_to_wallet=False)
-        res2 = self.test_send(from_wallet=w0, to_wallet=w1, amount=1, conf_target=1, estimate_mode="economical", add_to_wallet=False)
+        res1 = self.test_send(from_wallet=w0, to_wallet=w1, amount=1, arg_fee_rate=1, add_to_wallet=False)
+        res2 = self.test_send(from_wallet=w0, to_wallet=w1, amount=1, fee_rate=1, add_to_wallet=False)
         assert_equal(self.nodes[1].decodepsbt(res1["psbt"])["fee"], self.nodes[1].decodepsbt(res2["psbt"])["fee"])
 
-        res = self.test_send(from_wallet=w0, to_wallet=w1, amount=1, conf_target=0.00007, estimate_mode="btc/kb", add_to_wallet=False)
+        # Passing conf_target 0, estimate_mode "" as placeholder arguments should allow fee_rate to apply.
+        res = self.test_send(from_wallet=w0, to_wallet=w1, amount=1, conf_target=0, estimate_mode="", fee_rate=7, add_to_wallet=False)
         fee = self.nodes[1].decodepsbt(res["psbt"])["fee"]
         assert_fee_amount(fee, Decimal(len(res["hex"]) / 2), Decimal("0.00007"))
 
-        res = self.test_send(from_wallet=w0, to_wallet=w1, amount=1, conf_target=2, estimate_mode="sat/b", add_to_wallet=False)
+        res = self.test_send(from_wallet=w0, to_wallet=w1, amount=1, fee_rate=2, add_to_wallet=False)
         fee = self.nodes[1].decodepsbt(res["psbt"])["fee"]
         assert_fee_amount(fee, Decimal(len(res["hex"]) / 2), Decimal("0.00002"))
 
-        res = self.test_send(from_wallet=w0, to_wallet=w1, amount=1, arg_conf_target=0.00004531, arg_estimate_mode="btc/kb", add_to_wallet=False)
+        # Passing conf_target 0, estimate_mode "" as placeholder arguments should allow fee_rate to apply.
+        res = self.test_send(from_wallet=w0, to_wallet=w1, amount=1, arg_conf_target=0, arg_estimate_mode="", arg_fee_rate=4.531, add_to_wallet=False)
         fee = self.nodes[1].decodepsbt(res["psbt"])["fee"]
         assert_fee_amount(fee, Decimal(len(res["hex"]) / 2), Decimal("0.00004531"))
 
-        res = self.test_send(from_wallet=w0, to_wallet=w1, amount=1, arg_conf_target=3, arg_estimate_mode="sat/b", add_to_wallet=False)
+        res = self.test_send(from_wallet=w0, to_wallet=w1, amount=1, arg_fee_rate=3, add_to_wallet=False)
         fee = self.nodes[1].decodepsbt(res["psbt"])["fee"]
         assert_fee_amount(fee, Decimal(len(res["hex"]) / 2), Decimal("0.00003"))
 
-        # TODO: This test should pass with all modes, e.g. with the next line uncommented, for consistency with the other explicit feerate RPCs.
-        # for mode in ["unset", "economical", "conservative", "btc/kb", "sat/b"]:
-        for mode in ["btc/kb", "sat/b"]:
-            self.test_send(from_wallet=w0, to_wallet=w1, amount=1, conf_target=-1, estimate_mode=mode,
-                expect_error=(-3, "Amount out of range"))
-            self.test_send(from_wallet=w0, to_wallet=w1, amount=1, conf_target=0, estimate_mode=mode,
-                expect_error=(-4, "Fee rate (0.00000000 BTC/kB) is lower than the minimum fee rate setting (0.00001000 BTC/kB)"))
-
-        for mode in ["foo", Decimal("3.141592")]:
-            self.test_send(from_wallet=w0, to_wallet=w1, amount=1, conf_target=0.1, estimate_mode=mode,
-                expect_error=(-8, "Invalid estimate_mode parameter"))
-            # TODO: these 2 equivalent sends with an invalid estimate_mode arg should both fail, but they do not...why?
-            # self.test_send(from_wallet=w0, to_wallet=w1, amount=1, arg_conf_target=0.1, arg_estimate_mode=mode,
-            #     expect_error=(-8, "Invalid estimate_mode parameter"))
-            # assert_raises_rpc_error(-8, "Invalid estimate_mode parameter", lambda: w0.send({w1.getnewaddress(): 1}, 0.1, mode))
-
-        # TODO: These tests should pass for consistency with the other explicit feerate RPCs, but they do not.
-        # for mode in ["unset", "economical", "conservative", "btc/kb", "sat/b"]:
-        #     self.log.debug("{}".format(mode))
-        #     for k, v in {"string": "", "object": {"foo": "bar"}}.items():
-        #         self.test_send(from_wallet=w0, to_wallet=w1, amount=1, conf_target=v, estimate_mode=mode,
-        #             expect_error=(-3, "Expected type number for conf_target, got {}".format(k)))
-
-        # TODO: error should use sat/B instead of BTC/kB if sat/B is selected.
+        # Test that passing fee_rate as both an argument and an option raises.
+        self.test_send(from_wallet=w0, to_wallet=w1, amount=1, arg_fee_rate=1, fee_rate=1, add_to_wallet=False,
+                       expect_error=(-8, "Pass the fee_rate either as an argument, or in the options object, but not both"))
+
+        assert_raises_rpc_error(-8, "Use fee_rate (sat/vB) instead of feeRate", w0.send, {w1.getnewaddress(): 1}, 6, "conservative", 1, {"feeRate": 0.01})
+
+        assert_raises_rpc_error(-3, "Unexpected key totalFee", w0.send, {w1.getnewaddress(): 1}, 6, "conservative", 1, {"totalFee": 0.01})
+
+        for target, mode in product([-1, 0, 1009], ["economical", "conservative"]):
+            self.test_send(from_wallet=w0, to_wallet=w1, amount=1, conf_target=target, estimate_mode=mode,
+                expect_error=(-8, "Invalid conf_target, must be between 1 and 1008"))  # max value of 1008 per src/policy/fees.h
+        msg = 'Invalid estimate_mode parameter, must be one of: "unset", "economical", "conservative"'
+        for target, mode in product([-1, 0], ["btc/kb", "sat/b"]):
+            self.test_send(from_wallet=w0, to_wallet=w1, amount=1, conf_target=target, estimate_mode=mode, expect_error=(-8, msg))
+        for mode in ["", "foo", Decimal("3.141592")]:
+            self.test_send(from_wallet=w0, to_wallet=w1, amount=1, conf_target=0.1, estimate_mode=mode, expect_error=(-8, msg))
+            self.test_send(from_wallet=w0, to_wallet=w1, amount=1, arg_conf_target=0.1, arg_estimate_mode=mode, expect_error=(-8, msg))
+            assert_raises_rpc_error(-8, msg, w0.send, {w1.getnewaddress(): 1}, 0.1, mode)
+
+        for mode in ["economical", "conservative", "btc/kb", "sat/b"]:
+            self.log.debug("{}".format(mode))
+            for k, v in {"string": "true", "object": {"foo": "bar"}}.items():
+                self.test_send(from_wallet=w0, to_wallet=w1, amount=1, conf_target=v, estimate_mode=mode,
+                    expect_error=(-3, "Expected type number for conf_target, got {}".format(k)))
+
         # Test setting explicit fee rate just below the minimum.
-        for unit, fee_rate in {"sat/B": 0.99999999, "BTC/kB": 0.00000999}.items():
-            self.log.info("Explicit fee rate raises RPC error 'fee rate too low' if conf_target {} and estimate_mode {} are passed".format(fee_rate, unit))
-            self.test_send(from_wallet=w0, to_wallet=w1, amount=1, conf_target=fee_rate, estimate_mode=unit,
-                expect_error=(-4, "Fee rate (0.00000999 BTC/kB) is lower than the minimum fee rate setting (0.00001000 BTC/kB)"))
-
-        self.log.info("Explicit fee rate raises RPC error if estimate_mode is passed without a conf_target")
-        for unit, fee_rate in {"sat/B": 100, "BTC/kB": 0.001}.items():
-            self.test_send(from_wallet=w0, to_wallet=w1, amount=1, estimate_mode=unit,
-                expect_error=(-8, "Selected estimate_mode {} requires a fee rate to be specified in conf_target".format(unit)))
+        self.log.info("Explicit fee rate raises RPC error 'fee rate too low' if fee_rate of 0.99999999 is passed")
+        self.test_send(from_wallet=w0, to_wallet=w1, amount=1, fee_rate=0.99999999,
+            expect_error=(-4, "Fee rate (0.999 sat/vB) is lower than the minimum fee rate setting (1.000 sat/vB)"))
 
         # TODO: Return hex if fee rate is below -maxmempool
         # res = self.test_send(from_wallet=w0, to_wallet=w1, amount=1, conf_target=0.1, estimate_mode="sat/b", add_to_wallet=False)