diff --git a/src/Makefile.test.include b/src/Makefile.test.include
index 5a5c74c044..7df1ecb25d 100644
--- a/src/Makefile.test.include
+++ b/src/Makefile.test.include
@@ -139,6 +139,7 @@ BITCOIN_TESTS =\
   test/transaction_tests.cpp \
   test/txindex_tests.cpp \
   test/txrequest_tests.cpp \
+  test/txpackage_tests.cpp \
   test/txvalidation_tests.cpp \
   test/txvalidationcache_tests.cpp \
   test/uint256_tests.cpp \
diff --git a/src/rpc/rawtransaction.cpp b/src/rpc/rawtransaction.cpp
index 483717aa7a..fd18d4c96d 100644
--- a/src/rpc/rawtransaction.cpp
+++ b/src/rpc/rawtransaction.cpp
@@ -977,7 +977,7 @@ static RPCHelpMan testmempoolaccept()
         if (tx_result.m_result_type == MempoolAcceptResult::ResultType::VALID) {
             const CAmount fee = tx_result.m_base_fees.value();
             // Check that fee does not exceed maximum fee
-            const int64_t virtual_size = GetVirtualTransactionSize(*tx);
+            const int64_t virtual_size = tx_result.m_vsize.value();
             const CAmount max_raw_tx_fee = max_raw_tx_fee_rate.GetFee(virtual_size);
             if (max_raw_tx_fee && fee > max_raw_tx_fee) {
                 result_inner.pushKV("allowed", false);
diff --git a/src/test/txpackage_tests.cpp b/src/test/txpackage_tests.cpp
new file mode 100644
index 0000000000..537a6ccea1
--- /dev/null
+++ b/src/test/txpackage_tests.cpp
@@ -0,0 +1,117 @@
+// Copyright (c) 2021 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <consensus/validation.h>
+#include <key_io.h>
+#include <policy/packages.h>
+#include <policy/policy.h>
+#include <primitives/transaction.h>
+#include <script/script.h>
+#include <script/standard.h>
+#include <test/util/setup_common.h>
+#include <validation.h>
+
+#include <boost/test/unit_test.hpp>
+
+BOOST_AUTO_TEST_SUITE(txpackage_tests)
+
+// Create placeholder transactions that have no meaning.
+inline CTransactionRef create_placeholder_tx(size_t num_inputs, size_t num_outputs)
+{
+    CMutableTransaction mtx = CMutableTransaction();
+    mtx.vin.resize(num_inputs);
+    mtx.vout.resize(num_outputs);
+    auto random_script = CScript() << ToByteVector(InsecureRand256()) << ToByteVector(InsecureRand256());
+    for (size_t i{0}; i < num_inputs; ++i) {
+        mtx.vin[i].prevout.hash = InsecureRand256();
+        mtx.vin[i].prevout.n = 0;
+        mtx.vin[i].scriptSig = random_script;
+    }
+    for (size_t o{0}; o < num_outputs; ++o) {
+        mtx.vout[o].nValue = 1 * CENT;
+        mtx.vout[o].scriptPubKey = random_script;
+    }
+    return MakeTransactionRef(mtx);
+}
+
+BOOST_FIXTURE_TEST_CASE(package_sanitization_tests, TestChain100Setup)
+{
+    // Packages can't have more than 25 transactions.
+    Package package_too_many;
+    package_too_many.reserve(MAX_PACKAGE_COUNT + 1);
+    for (size_t i{0}; i < MAX_PACKAGE_COUNT + 1; ++i) {
+        package_too_many.emplace_back(create_placeholder_tx(1, 1));
+    }
+    PackageValidationState state_too_many;
+    BOOST_CHECK(!CheckPackage(package_too_many, state_too_many));
+    BOOST_CHECK_EQUAL(state_too_many.GetResult(), PackageValidationResult::PCKG_POLICY);
+    BOOST_CHECK_EQUAL(state_too_many.GetRejectReason(), "package-too-many-transactions");
+
+    // Packages can't have a total size of more than 101KvB.
+    CTransactionRef large_ptx = create_placeholder_tx(150, 150);
+    Package package_too_large;
+    auto size_large = GetVirtualTransactionSize(*large_ptx);
+    size_t total_size{0};
+    while (total_size <= MAX_PACKAGE_SIZE * 1000) {
+        package_too_large.push_back(large_ptx);
+        total_size += size_large;
+    }
+    BOOST_CHECK(package_too_large.size() <= MAX_PACKAGE_COUNT);
+    PackageValidationState state_too_large;
+    BOOST_CHECK(!CheckPackage(package_too_large, state_too_large));
+    BOOST_CHECK_EQUAL(state_too_large.GetResult(), PackageValidationResult::PCKG_POLICY);
+    BOOST_CHECK_EQUAL(state_too_large.GetRejectReason(), "package-too-large");
+}
+
+BOOST_FIXTURE_TEST_CASE(package_validation_tests, TestChain100Setup)
+{
+    LOCK(cs_main);
+    unsigned int initialPoolSize = m_node.mempool->size();
+
+    // Parent and Child Package
+    CKey parent_key;
+    parent_key.MakeNewKey(true);
+    CScript parent_locking_script = GetScriptForDestination(PKHash(parent_key.GetPubKey()));
+    auto mtx_parent = CreateValidMempoolTransaction(/* input_transaction */ m_coinbase_txns[0], /* vout */ 0,
+                                                    /* input_height */ 0, /* input_signing_key */ coinbaseKey,
+                                                    /* output_destination */ parent_locking_script,
+                                                    /* output_amount */ CAmount(49 * COIN), /* submit */ false);
+    CTransactionRef tx_parent = MakeTransactionRef(mtx_parent);
+
+    CKey child_key;
+    child_key.MakeNewKey(true);
+    CScript child_locking_script = GetScriptForDestination(PKHash(child_key.GetPubKey()));
+    auto mtx_child = CreateValidMempoolTransaction(/* input_transaction */ tx_parent, /* vout */ 0,
+                                                   /* input_height */ 101, /* input_signing_key */ parent_key,
+                                                   /* output_destination */ child_locking_script,
+                                                   /* output_amount */ CAmount(48 * COIN), /* submit */ false);
+    CTransactionRef tx_child = MakeTransactionRef(mtx_child);
+    const auto result_parent_child = ProcessNewPackage(m_node.chainman->ActiveChainstate(), *m_node.mempool, {tx_parent, tx_child}, /* test_accept */ true);
+    BOOST_CHECK_MESSAGE(result_parent_child.m_state.IsValid(),
+                        "Package validation unexpectedly failed: " << result_parent_child.m_state.GetRejectReason());
+    auto it_parent = result_parent_child.m_tx_results.find(tx_parent->GetWitnessHash());
+    auto it_child = result_parent_child.m_tx_results.find(tx_child->GetWitnessHash());
+    BOOST_CHECK(it_parent != result_parent_child.m_tx_results.end());
+    BOOST_CHECK_MESSAGE(it_parent->second.m_state.IsValid(),
+                        "Package validation unexpectedly failed: " << it_parent->second.m_state.GetRejectReason());
+    BOOST_CHECK(it_child != result_parent_child.m_tx_results.end());
+    BOOST_CHECK_MESSAGE(it_child->second.m_state.IsValid(),
+                        "Package validation unexpectedly failed: " << it_child->second.m_state.GetRejectReason());
+
+
+    // A single, giant transaction submitted through ProcessNewPackage fails on single tx policy.
+    CTransactionRef giant_ptx = create_placeholder_tx(999, 999);
+    BOOST_CHECK(GetVirtualTransactionSize(*giant_ptx) > MAX_PACKAGE_SIZE * 1000);
+    auto result_single_large = ProcessNewPackage(m_node.chainman->ActiveChainstate(), *m_node.mempool, {giant_ptx}, /* test_accept */ true);
+    BOOST_CHECK(result_single_large.m_state.IsInvalid());
+    BOOST_CHECK_EQUAL(result_single_large.m_state.GetResult(), PackageValidationResult::PCKG_TX);
+    BOOST_CHECK_EQUAL(result_single_large.m_state.GetRejectReason(), "transaction failed");
+    auto it_giant_tx = result_single_large.m_tx_results.find(giant_ptx->GetWitnessHash());
+    BOOST_CHECK(it_giant_tx != result_single_large.m_tx_results.end());
+    BOOST_CHECK_EQUAL(it_giant_tx->second.m_state.GetRejectReason(), "tx-size");
+
+    // Check that mempool size hasn't changed.
+    BOOST_CHECK_EQUAL(m_node.mempool->size(), initialPoolSize);
+}
+BOOST_AUTO_TEST_SUITE_END()
diff --git a/src/test/txvalidation_tests.cpp b/src/test/txvalidation_tests.cpp
index ade9e210f2..8d25f5331d 100644
--- a/src/test/txvalidation_tests.cpp
+++ b/src/test/txvalidation_tests.cpp
@@ -50,99 +50,4 @@ BOOST_FIXTURE_TEST_CASE(tx_mempool_reject_coinbase, TestChain100Setup)
     BOOST_CHECK_EQUAL(result.m_state.GetRejectReason(), "coinbase");
     BOOST_CHECK(result.m_state.GetResult() == TxValidationResult::TX_CONSENSUS);
 }
-
-// Create placeholder transactions that have no meaning.
-inline CTransactionRef create_placeholder_tx(size_t num_inputs, size_t num_outputs)
-{
-    CMutableTransaction mtx = CMutableTransaction();
-    mtx.vin.resize(num_inputs);
-    mtx.vout.resize(num_outputs);
-    auto random_script = CScript() << ToByteVector(InsecureRand256()) << ToByteVector(InsecureRand256());
-    for (size_t i{0}; i < num_inputs; ++i) {
-        mtx.vin[i].prevout.hash = InsecureRand256();
-        mtx.vin[i].prevout.n = 0;
-        mtx.vin[i].scriptSig = random_script;
-    }
-    for (size_t o{0}; o < num_outputs; ++o) {
-        mtx.vout[o].nValue = 1 * CENT;
-        mtx.vout[o].scriptPubKey = random_script;
-    }
-    return MakeTransactionRef(mtx);
-}
-
-BOOST_FIXTURE_TEST_CASE(package_tests, TestChain100Setup)
-{
-    LOCK(cs_main);
-    unsigned int initialPoolSize = m_node.mempool->size();
-
-    // Parent and Child Package
-    CKey parent_key;
-    parent_key.MakeNewKey(true);
-    CScript parent_locking_script = GetScriptForDestination(PKHash(parent_key.GetPubKey()));
-    auto mtx_parent = CreateValidMempoolTransaction(/* input_transaction */ m_coinbase_txns[0], /* vout */ 0,
-                                                    /* input_height */ 0, /* input_signing_key */ coinbaseKey,
-                                                    /* output_destination */ parent_locking_script,
-                                                    /* output_amount */ CAmount(49 * COIN), /* submit */ false);
-    CTransactionRef tx_parent = MakeTransactionRef(mtx_parent);
-
-    CKey child_key;
-    child_key.MakeNewKey(true);
-    CScript child_locking_script = GetScriptForDestination(PKHash(child_key.GetPubKey()));
-    auto mtx_child = CreateValidMempoolTransaction(/* input_transaction */ tx_parent, /* vout */ 0,
-                                                   /* input_height */ 101, /* input_signing_key */ parent_key,
-                                                   /* output_destination */ child_locking_script,
-                                                   /* output_amount */ CAmount(48 * COIN), /* submit */ false);
-    CTransactionRef tx_child = MakeTransactionRef(mtx_child);
-    const auto result_parent_child = ProcessNewPackage(m_node.chainman->ActiveChainstate(), *m_node.mempool, {tx_parent, tx_child}, /* test_accept */ true);
-    BOOST_CHECK_MESSAGE(result_parent_child.m_state.IsValid(),
-                        "Package validation unexpectedly failed: " << result_parent_child.m_state.GetRejectReason());
-    auto it_parent = result_parent_child.m_tx_results.find(tx_parent->GetWitnessHash());
-    auto it_child = result_parent_child.m_tx_results.find(tx_child->GetWitnessHash());
-    BOOST_CHECK(it_parent != result_parent_child.m_tx_results.end());
-    BOOST_CHECK_MESSAGE(it_parent->second.m_state.IsValid(),
-                        "Package validation unexpectedly failed: " << it_parent->second.m_state.GetRejectReason());
-    BOOST_CHECK(it_child != result_parent_child.m_tx_results.end());
-    BOOST_CHECK_MESSAGE(it_child->second.m_state.IsValid(),
-                        "Package validation unexpectedly failed: " << it_child->second.m_state.GetRejectReason());
-
-    // Packages can't have more than 25 transactions.
-    Package package_too_many;
-    package_too_many.reserve(MAX_PACKAGE_COUNT + 1);
-    for (size_t i{0}; i < MAX_PACKAGE_COUNT + 1; ++i) {
-        package_too_many.emplace_back(create_placeholder_tx(1, 1));
-    }
-    auto result_too_many = ProcessNewPackage(m_node.chainman->ActiveChainstate(), *m_node.mempool, package_too_many, /* test_accept */ true);
-    BOOST_CHECK(result_too_many.m_state.IsInvalid());
-    BOOST_CHECK_EQUAL(result_too_many.m_state.GetResult(), PackageValidationResult::PCKG_POLICY);
-    BOOST_CHECK_EQUAL(result_too_many.m_state.GetRejectReason(), "package-too-many-transactions");
-
-    // Packages can't have a total size of more than 101KvB.
-    CTransactionRef large_ptx = create_placeholder_tx(150, 150);
-    Package package_too_large;
-    auto size_large = GetVirtualTransactionSize(*large_ptx);
-    size_t total_size{0};
-    while (total_size <= MAX_PACKAGE_SIZE * 1000) {
-        package_too_large.push_back(large_ptx);
-        total_size += size_large;
-    }
-    BOOST_CHECK(package_too_large.size() <= MAX_PACKAGE_COUNT);
-    auto result_too_large = ProcessNewPackage(m_node.chainman->ActiveChainstate(), *m_node.mempool, package_too_large, /* test_accept */ true);
-    BOOST_CHECK(result_too_large.m_state.IsInvalid());
-    BOOST_CHECK_EQUAL(result_too_large.m_state.GetResult(), PackageValidationResult::PCKG_POLICY);
-    BOOST_CHECK_EQUAL(result_too_large.m_state.GetRejectReason(), "package-too-large");
-
-    // A single, giant transaction submitted through ProcessNewPackage fails on single tx policy.
-    CTransactionRef giant_ptx = create_placeholder_tx(999, 999);
-    BOOST_CHECK(GetVirtualTransactionSize(*giant_ptx) > MAX_PACKAGE_SIZE * 1000);
-    auto result_single_large = ProcessNewPackage(m_node.chainman->ActiveChainstate(), *m_node.mempool, {giant_ptx}, /* test_accept */ true);
-    BOOST_CHECK(result_single_large.m_state.IsInvalid());
-    BOOST_CHECK_EQUAL(result_single_large.m_state.GetResult(), PackageValidationResult::PCKG_TX);
-    BOOST_CHECK_EQUAL(result_single_large.m_state.GetRejectReason(), "transaction failed");
-    auto it_giant_tx = result_single_large.m_tx_results.find(giant_ptx->GetWitnessHash());
-    BOOST_CHECK(it_giant_tx != result_single_large.m_tx_results.end());
-    BOOST_CHECK_EQUAL(it_giant_tx->second.m_state.GetRejectReason(), "tx-size");
-
-    // Check that mempool size hasn't changed.
-    BOOST_CHECK_EQUAL(m_node.mempool->size(), initialPoolSize);
-}
 BOOST_AUTO_TEST_SUITE_END()
diff --git a/src/validation.cpp b/src/validation.cpp
index 207cdc8233..9a3375fea9 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -450,7 +450,36 @@ public:
         /** Whether we allow transactions to replace mempool transactions by BIP125 rules. If false,
          * any transaction spending the same inputs as a transaction in the mempool is considered
          * a conflict. */
-        const bool m_allow_bip125_replacement{true};
+        const bool m_allow_bip125_replacement;
+
+        /** Parameters for single transaction mempool validation. */
+        static ATMPArgs SingleAccept(const CChainParams& chainparams, int64_t accept_time,
+                                     bool bypass_limits, std::vector<COutPoint>& coins_to_uncache,
+                                     bool test_accept) {
+            return ATMPArgs{/* m_chainparams */ chainparams,
+                            /* m_accept_time */ accept_time,
+                            /* m_bypass_limits */ bypass_limits,
+                            /* m_coins_to_uncache */ coins_to_uncache,
+                            /* m_test_accept */ test_accept,
+                            /* m_allow_bip125_replacement */ true,
+            };
+        }
+
+        /** Parameters for test package mempool validation through testmempoolaccept. */
+        static ATMPArgs PackageTestAccept(const CChainParams& chainparams, int64_t accept_time,
+                                          std::vector<COutPoint>& coins_to_uncache) {
+            return ATMPArgs{/* m_chainparams */ chainparams,
+                            /* m_accept_time */ accept_time,
+                            /* m_bypass_limits */ false,
+                            /* m_coins_to_uncache */ coins_to_uncache,
+                            /* m_test_accept */ true,
+                            /* m_allow_bip125_replacement */ false,
+            };
+        }
+
+        // No default ctor to avoid exposing details to clients and allowing the possibility of
+        // mixing up the order of the arguments. Use static functions above instead.
+        ATMPArgs() = delete;
     };
 
     // Single transaction acceptance
@@ -468,13 +497,29 @@ private:
     // of checking a given transaction.
     struct Workspace {
         explicit Workspace(const CTransactionRef& ptx) : m_ptx(ptx), m_hash(ptx->GetHash()) {}
+        /** Txids of mempool transactions that this transaction directly conflicts with. */
         std::set<uint256> m_conflicts;
+        /** Iterators to mempool entries that this transaction directly conflicts with. */
+        CTxMemPool::setEntries m_iters_conflicting;
+        /** Iterators to all mempool entries that would be replaced by this transaction, including
+         * those it directly conflicts with and their descendants. */
         CTxMemPool::setEntries m_all_conflicting;
+        /** All mempool ancestors of this transaction. */
         CTxMemPool::setEntries m_ancestors;
+        /** Mempool entry constructed for this transaction. Constructed in PreChecks() but not
+         * inserted into the mempool until Finalize(). */
         std::unique_ptr<CTxMemPoolEntry> m_entry;
+        /** Pointers to the transactions that have been removed from the mempool and replaced by
+         * this transaction, used to return to the MemPoolAccept caller. Only populated if
+         * validation is successful and the original transactions are removed. */
         std::list<CTransactionRef> m_replaced_transactions;
 
+        /** Virtual size of the transaction as used by the mempool, calculated using serialized size
+         * of the transaction and sigops. */
+        int64_t m_vsize;
+        /** Fees paid by this transaction: total input amounts subtracted by total output amounts. */
         CAmount m_base_fees;
+        /** Base fees + any fee delta set by the user with prioritisetransaction. */
         CAmount m_modified_fees;
         /** Total modified fees of all transactions being replaced. */
         CAmount m_conflicting_fees{0};
@@ -482,8 +527,12 @@ private:
         size_t m_conflicting_size{0};
 
         const CTransactionRef& m_ptx;
+        /** Txid. */
         const uint256& m_hash;
         TxValidationState m_state;
+        /** A temporary cache containing serialized transaction data for signature verification.
+         * Reused across PolicyScriptChecks and ConsensusScriptChecks. */
+        PrecomputedTransactionData m_precomputed_txdata;
     };
 
     // Run the policy checks on a given transaction, excluding any script checks.
@@ -492,15 +541,23 @@ private:
     // only tests that are fast should be done here (to avoid CPU DoS).
     bool PreChecks(ATMPArgs& args, Workspace& ws) EXCLUSIVE_LOCKS_REQUIRED(cs_main, m_pool.cs);
 
+    // Run checks for mempool replace-by-fee.
+    bool ReplacementChecks(Workspace& ws) EXCLUSIVE_LOCKS_REQUIRED(cs_main, m_pool.cs);
+
+    // Enforce package mempool ancestor/descendant limits (distinct from individual
+    // ancestor/descendant limits done in PreChecks).
+    bool PackageMempoolChecks(const std::vector<CTransactionRef>& txns,
+                              PackageValidationState& package_state) EXCLUSIVE_LOCKS_REQUIRED(cs_main, m_pool.cs);
+
     // Run the script checks using our policy flags. As this can be slow, we should
     // only invoke this on transactions that have otherwise passed policy checks.
-    bool PolicyScriptChecks(const ATMPArgs& args, Workspace& ws, PrecomputedTransactionData& txdata) EXCLUSIVE_LOCKS_REQUIRED(cs_main, m_pool.cs);
+    bool PolicyScriptChecks(const ATMPArgs& args, Workspace& ws) EXCLUSIVE_LOCKS_REQUIRED(cs_main, m_pool.cs);
 
     // Re-run the script checks, using consensus flags, and try to cache the
     // result in the scriptcache. This should be done after
     // PolicyScriptChecks(). This requires that all inputs either be in our
     // utxo set or in the mempool.
-    bool ConsensusScriptChecks(const ATMPArgs& args, Workspace& ws, PrecomputedTransactionData &txdata) EXCLUSIVE_LOCKS_REQUIRED(cs_main, m_pool.cs);
+    bool ConsensusScriptChecks(const ATMPArgs& args, Workspace& ws) EXCLUSIVE_LOCKS_REQUIRED(cs_main, m_pool.cs);
 
     // Try to add the transaction to the mempool, removing any conflicts first.
     // Returns true if the transaction is in the mempool after any size
@@ -536,6 +593,9 @@ private:
     // in-mempool conflicts; see below).
     size_t m_limit_descendants;
     size_t m_limit_descendant_size;
+
+    /** Whether the transaction(s) would replace any mempool transactions. If so, RBF rules apply. */
+    bool m_rbf{false};
 };
 
 bool MemPoolAccept::PreChecks(ATMPArgs& args, Workspace& ws)
@@ -551,13 +611,7 @@ bool MemPoolAccept::PreChecks(ATMPArgs& args, Workspace& ws)
 
     // Alias what we need out of ws
     TxValidationState& state = ws.m_state;
-    std::set<uint256>& setConflicts = ws.m_conflicts;
-    CTxMemPool::setEntries& allConflicting = ws.m_all_conflicting;
-    CTxMemPool::setEntries& setAncestors = ws.m_ancestors;
     std::unique_ptr<CTxMemPoolEntry>& entry = ws.m_entry;
-    CAmount& nModifiedFees = ws.m_modified_fees;
-    CAmount& nConflictingFees = ws.m_conflicting_fees;
-    size_t& nConflictingSize = ws.m_conflicting_size;
 
     if (!CheckTransaction(tx, state)) {
         return false; // state filled in by CheckTransaction
@@ -603,7 +657,7 @@ bool MemPoolAccept::PreChecks(ATMPArgs& args, Workspace& ws)
                 // Transaction conflicts with a mempool tx, but we're not allowing replacements.
                 return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY, "bip125-replacement-disallowed");
             }
-            if (!setConflicts.count(ptxConflicting->GetHash()))
+            if (!ws.m_conflicts.count(ptxConflicting->GetHash()))
             {
                 // Transactions that don't explicitly signal replaceability are
                 // *not* replaceable with the current logic, even if one of their
@@ -616,7 +670,7 @@ bool MemPoolAccept::PreChecks(ATMPArgs& args, Workspace& ws)
                     return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY, "txn-mempool-conflict");
                 }
 
-                setConflicts.insert(ptxConflicting->GetHash());
+                ws.m_conflicts.insert(ptxConflicting->GetHash());
             }
         }
     }
@@ -680,9 +734,9 @@ bool MemPoolAccept::PreChecks(ATMPArgs& args, Workspace& ws)
 
     int64_t nSigOpsCost = GetTransactionSigOpCost(tx, m_view, STANDARD_SCRIPT_VERIFY_FLAGS);
 
-    // nModifiedFees includes any fee deltas from PrioritiseTransaction
-    nModifiedFees = ws.m_base_fees;
-    m_pool.ApplyDelta(hash, nModifiedFees);
+    // ws.m_modified_fees includes any fee deltas from PrioritiseTransaction
+    ws.m_modified_fees = ws.m_base_fees;
+    m_pool.ApplyDelta(hash, ws.m_modified_fees);
 
     // Keep track of transactions that spend a coinbase, which we re-scan
     // during reorgs to ensure COINBASE_MATURITY is still met.
@@ -697,7 +751,7 @@ bool MemPoolAccept::PreChecks(ATMPArgs& args, Workspace& ws)
 
     entry.reset(new CTxMemPoolEntry(ptx, ws.m_base_fees, nAcceptTime, m_active_chainstate.m_chain.Height(),
             fSpendsCoinbase, nSigOpsCost, lp));
-    unsigned int nSize = entry->GetTxSize();
+    ws.m_vsize = entry->GetTxSize();
 
     if (nSigOpsCost > MAX_STANDARD_TX_SIGOPS_COST)
         return state.Invalid(TxValidationResult::TX_NOT_STANDARD, "bad-txns-too-many-sigops",
@@ -705,11 +759,11 @@ bool MemPoolAccept::PreChecks(ATMPArgs& args, Workspace& ws)
 
     // No transactions are allowed below minRelayTxFee except from disconnected
     // blocks
-    if (!bypass_limits && !CheckFeeRate(nSize, nModifiedFees, state)) return false;
+    if (!bypass_limits && !CheckFeeRate(ws.m_vsize, ws.m_modified_fees, state)) return false;
 
-    const CTxMemPool::setEntries setIterConflicting = m_pool.GetIterSet(setConflicts);
+    ws.m_iters_conflicting = m_pool.GetIterSet(ws.m_conflicts);
     // Calculate in-mempool ancestors, up to a limit.
-    if (setConflicts.size() == 1) {
+    if (ws.m_conflicts.size() == 1) {
         // In general, when we receive an RBF transaction with mempool conflicts, we want to know whether we
         // would meet the chain limits after the conflicts have been removed. However, there isn't a practical
         // way to do this short of calculating the ancestor and descendant sets with an overlay cache of
@@ -737,16 +791,16 @@ bool MemPoolAccept::PreChecks(ATMPArgs& args, Workspace& ws)
         // the ancestor limits should be the same for both our new transaction and any conflicts).
         // We don't bother incrementing m_limit_descendants by the full removal count as that limit never comes
         // into force here (as we're only adding a single transaction).
-        assert(setIterConflicting.size() == 1);
-        CTxMemPool::txiter conflict = *setIterConflicting.begin();
+        assert(ws.m_iters_conflicting.size() == 1);
+        CTxMemPool::txiter conflict = *ws.m_iters_conflicting.begin();
 
         m_limit_descendants += 1;
         m_limit_descendant_size += conflict->GetSizeWithDescendants();
     }
 
     std::string errString;
-    if (!m_pool.CalculateMemPoolAncestors(*entry, setAncestors, m_limit_ancestors, m_limit_ancestor_size, m_limit_descendants, m_limit_descendant_size, errString)) {
-        setAncestors.clear();
+    if (!m_pool.CalculateMemPoolAncestors(*entry, ws.m_ancestors, m_limit_ancestors, m_limit_ancestor_size, m_limit_descendants, m_limit_descendant_size, errString)) {
+        ws.m_ancestors.clear();
         // If CalculateMemPoolAncestors fails second time, we want the original error string.
         std::string dummy_err_string;
         // Contracting/payment channels CPFP carve-out:
@@ -760,60 +814,85 @@ bool MemPoolAccept::PreChecks(ATMPArgs& args, Workspace& ws)
         // to be secure by simply only having two immediately-spendable
         // outputs - one for each counterparty. For more info on the uses for
         // this, see https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2018-November/016518.html
-        if (nSize >  EXTRA_DESCENDANT_TX_SIZE_LIMIT ||
-                !m_pool.CalculateMemPoolAncestors(*entry, setAncestors, 2, m_limit_ancestor_size, m_limit_descendants + 1, m_limit_descendant_size + EXTRA_DESCENDANT_TX_SIZE_LIMIT, dummy_err_string)) {
+        if (ws.m_vsize > EXTRA_DESCENDANT_TX_SIZE_LIMIT ||
+                !m_pool.CalculateMemPoolAncestors(*entry, ws.m_ancestors, 2, m_limit_ancestor_size, m_limit_descendants + 1, m_limit_descendant_size + EXTRA_DESCENDANT_TX_SIZE_LIMIT, dummy_err_string)) {
             return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY, "too-long-mempool-chain", errString);
         }
     }
 
     // A transaction that spends outputs that would be replaced by it is invalid. Now
     // that we have the set of all ancestors we can detect this
-    // pathological case by making sure setConflicts and setAncestors don't
+    // pathological case by making sure ws.m_conflicts and ws.m_ancestors don't
     // intersect.
-    if (const auto err_string{EntriesAndTxidsDisjoint(setAncestors, setConflicts, hash)}) {
+    if (const auto err_string{EntriesAndTxidsDisjoint(ws.m_ancestors, ws.m_conflicts, hash)}) {
         // We classify this as a consensus error because a transaction depending on something it
         // conflicts with would be inconsistent.
         return state.Invalid(TxValidationResult::TX_CONSENSUS, "bad-txns-spends-conflicting-tx", *err_string);
     }
 
+    m_rbf = !ws.m_conflicts.empty();
+    return true;
+}
 
-    if (!setConflicts.empty()) {
-        CFeeRate newFeeRate(nModifiedFees, nSize);
-        // It's possible that the replacement pays more fees than its direct conflicts but not more
-        // than all conflicts (i.e. the direct conflicts have high-fee descendants). However, if the
-        // replacement doesn't pay more fees than its direct conflicts, then we can be sure it's not
-        // more economically rational to mine. Before we go digging through the mempool for all
-        // transactions that would need to be removed (direct conflicts and all descendants), check
-        // that the replacement transaction pays more than its direct conflicts.
-        if (const auto err_string{PaysMoreThanConflicts(setIterConflicting, newFeeRate, hash)}) {
-            return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY, "insufficient fee", *err_string);
-        }
+bool MemPoolAccept::ReplacementChecks(Workspace& ws)
+{
+    AssertLockHeld(cs_main);
+    AssertLockHeld(m_pool.cs);
 
-        // Calculate all conflicting entries and enforce BIP125 Rule #5.
-        if (const auto err_string{GetEntriesForConflicts(tx, m_pool, setIterConflicting, allConflicting)}) {
-            return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY,
-                                 "too many potential replacements", *err_string);
-        }
-        // Enforce BIP125 Rule #2.
-        if (const auto err_string{HasNoNewUnconfirmed(tx, m_pool, setIterConflicting)}) {
-            return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY,
-                                 "replacement-adds-unconfirmed", *err_string);
-        }
+    const CTransaction& tx = *ws.m_ptx;
+    const uint256& hash = ws.m_hash;
+    TxValidationState& state = ws.m_state;
 
-        // Check if it's economically rational to mine this transaction rather than the ones it
-        // replaces and pays for its own relay fees. Enforce BIP125 Rules #3 and #4.
-        for (CTxMemPool::txiter it : allConflicting) {
-            nConflictingFees += it->GetModifiedFee();
-            nConflictingSize += it->GetTxSize();
-        }
-        if (const auto err_string{PaysForRBF(nConflictingFees, nModifiedFees, nSize, ::incrementalRelayFee, hash)}) {
-            return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY, "insufficient fee", *err_string);
-        }
+    CFeeRate newFeeRate(ws.m_modified_fees, ws.m_vsize);
+    // It's possible that the replacement pays more fees than its direct conflicts but not more
+    // than all conflicts (i.e. the direct conflicts have high-fee descendants). However, if the
+    // replacement doesn't pay more fees than its direct conflicts, then we can be sure it's not
+    // more economically rational to mine. Before we go digging through the mempool for all
+    // transactions that would need to be removed (direct conflicts and all descendants), check
+    // that the replacement transaction pays more than its direct conflicts.
+    if (const auto err_string{PaysMoreThanConflicts(ws.m_iters_conflicting, newFeeRate, hash)}) {
+        return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY, "insufficient fee", *err_string);
+    }
+
+    // Calculate all conflicting entries and enforce BIP125 Rule #5.
+    if (const auto err_string{GetEntriesForConflicts(tx, m_pool, ws.m_iters_conflicting, ws.m_all_conflicting)}) {
+        return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY,
+                             "too many potential replacements", *err_string);
+    }
+    // Enforce BIP125 Rule #2.
+    if (const auto err_string{HasNoNewUnconfirmed(tx, m_pool, ws.m_iters_conflicting)}) {
+        return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY,
+                             "replacement-adds-unconfirmed", *err_string);
+    }
+    // Check if it's economically rational to mine this transaction rather than the ones it
+    // replaces and pays for its own relay fees. Enforce BIP125 Rules #3 and #4.
+    for (CTxMemPool::txiter it : ws.m_all_conflicting) {
+        ws.m_conflicting_fees += it->GetModifiedFee();
+        ws.m_conflicting_size += it->GetTxSize();
+    }
+    if (const auto err_string{PaysForRBF(ws.m_conflicting_fees, ws.m_modified_fees, ws.m_vsize,
+                                         ::incrementalRelayFee, hash)}) {
+        return state.Invalid(TxValidationResult::TX_MEMPOOL_POLICY, "insufficient fee", *err_string);
     }
     return true;
 }
 
-bool MemPoolAccept::PolicyScriptChecks(const ATMPArgs& args, Workspace& ws, PrecomputedTransactionData& txdata)
+bool MemPoolAccept::PackageMempoolChecks(const std::vector<CTransactionRef>& txns,
+                                         PackageValidationState& package_state)
+{
+    AssertLockHeld(cs_main);
+    AssertLockHeld(m_pool.cs);
+
+    std::string err_string;
+    if (!m_pool.CheckPackageLimits(txns, m_limit_ancestors, m_limit_ancestor_size, m_limit_descendants,
+                                   m_limit_descendant_size, err_string)) {
+        // This is a package-wide error, separate from an individual transaction error.
+        return package_state.Invalid(PackageValidationResult::PCKG_POLICY, "package-mempool-limits", err_string);
+    }
+   return true;
+}
+
+bool MemPoolAccept::PolicyScriptChecks(const ATMPArgs& args, Workspace& ws)
 {
     const CTransaction& tx = *ws.m_ptx;
     TxValidationState& state = ws.m_state;
@@ -822,13 +901,13 @@ bool MemPoolAccept::PolicyScriptChecks(const ATMPArgs& args, Workspace& ws, Prec
 
     // Check input scripts and signatures.
     // This is done last to help prevent CPU exhaustion denial-of-service attacks.
-    if (!CheckInputScripts(tx, state, m_view, scriptVerifyFlags, true, false, txdata)) {
+    if (!CheckInputScripts(tx, state, m_view, scriptVerifyFlags, true, false, ws.m_precomputed_txdata)) {
         // SCRIPT_VERIFY_CLEANSTACK requires SCRIPT_VERIFY_WITNESS, so we
         // need to turn both off, and compare against just turning off CLEANSTACK
         // to see if the failure is specifically due to witness validation.
         TxValidationState state_dummy; // Want reported failures to be from first CheckInputScripts
-        if (!tx.HasWitness() && CheckInputScripts(tx, state_dummy, m_view, scriptVerifyFlags & ~(SCRIPT_VERIFY_WITNESS | SCRIPT_VERIFY_CLEANSTACK), true, false, txdata) &&
-                !CheckInputScripts(tx, state_dummy, m_view, scriptVerifyFlags & ~SCRIPT_VERIFY_CLEANSTACK, true, false, txdata)) {
+        if (!tx.HasWitness() && CheckInputScripts(tx, state_dummy, m_view, scriptVerifyFlags & ~(SCRIPT_VERIFY_WITNESS | SCRIPT_VERIFY_CLEANSTACK), true, false, ws.m_precomputed_txdata) &&
+                !CheckInputScripts(tx, state_dummy, m_view, scriptVerifyFlags & ~SCRIPT_VERIFY_CLEANSTACK, true, false, ws.m_precomputed_txdata)) {
             // Only the witness is missing, so the transaction itself may be fine.
             state.Invalid(TxValidationResult::TX_WITNESS_STRIPPED,
                     state.GetRejectReason(), state.GetDebugMessage());
@@ -839,7 +918,7 @@ bool MemPoolAccept::PolicyScriptChecks(const ATMPArgs& args, Workspace& ws, Prec
     return true;
 }
 
-bool MemPoolAccept::ConsensusScriptChecks(const ATMPArgs& args, Workspace& ws, PrecomputedTransactionData& txdata)
+bool MemPoolAccept::ConsensusScriptChecks(const ATMPArgs& args, Workspace& ws)
 {
     const CTransaction& tx = *ws.m_ptx;
     const uint256& hash = ws.m_hash;
@@ -862,7 +941,8 @@ bool MemPoolAccept::ConsensusScriptChecks(const ATMPArgs& args, Workspace& ws, P
     // invalid blocks (using TestBlockValidity), however allowing such
     // transactions into the mempool can be exploited as a DoS attack.
     unsigned int currentBlockScriptVerifyFlags = GetBlockScriptFlags(m_active_chainstate.m_chain.Tip(), chainparams.GetConsensus());
-    if (!CheckInputsFromMempoolAndCache(tx, state, m_view, m_pool, currentBlockScriptVerifyFlags, txdata, m_active_chainstate.CoinsTip())) {
+    if (!CheckInputsFromMempoolAndCache(tx, state, m_view, m_pool, currentBlockScriptVerifyFlags,
+                                        ws.m_precomputed_txdata, m_active_chainstate.CoinsTip())) {
         return error("%s: BUG! PLEASE REPORT THIS! CheckInputScripts failed against latest-block but not STANDARD flags %s, %s",
                 __func__, hash.ToString(), state.ToString());
     }
@@ -877,24 +957,19 @@ bool MemPoolAccept::Finalize(const ATMPArgs& args, Workspace& ws)
     TxValidationState& state = ws.m_state;
     const bool bypass_limits = args.m_bypass_limits;
 
-    CTxMemPool::setEntries& allConflicting = ws.m_all_conflicting;
-    CTxMemPool::setEntries& setAncestors = ws.m_ancestors;
-    const CAmount& nModifiedFees = ws.m_modified_fees;
-    const CAmount& nConflictingFees = ws.m_conflicting_fees;
-    const size_t& nConflictingSize = ws.m_conflicting_size;
     std::unique_ptr<CTxMemPoolEntry>& entry = ws.m_entry;
 
     // Remove conflicting transactions from the mempool
-    for (CTxMemPool::txiter it : allConflicting)
+    for (CTxMemPool::txiter it : ws.m_all_conflicting)
     {
         LogPrint(BCLog::MEMPOOL, "replacing tx %s with %s for %s additional fees, %d delta bytes\n",
                 it->GetTx().GetHash().ToString(),
                 hash.ToString(),
-                FormatMoney(nModifiedFees - nConflictingFees),
-                (int)entry->GetTxSize() - (int)nConflictingSize);
+                FormatMoney(ws.m_modified_fees - ws.m_conflicting_fees),
+                (int)entry->GetTxSize() - (int)ws.m_conflicting_size);
         ws.m_replaced_transactions.push_back(it->GetSharedTx());
     }
-    m_pool.RemoveStaged(allConflicting, false, MemPoolRemovalReason::REPLACED);
+    m_pool.RemoveStaged(ws.m_all_conflicting, false, MemPoolRemovalReason::REPLACED);
 
     // This transaction should only count for fee estimation if:
     // - it's not being re-added during a reorg which bypasses typical mempool fee limits
@@ -903,7 +978,7 @@ bool MemPoolAccept::Finalize(const ATMPArgs& args, Workspace& ws)
     bool validForFeeEstimation = !bypass_limits && IsCurrentForFeeEstimation(m_active_chainstate) && m_pool.HasNoInputsOf(tx);
 
     // Store transaction in memory
-    m_pool.addUnchecked(*entry, setAncestors, validForFeeEstimation);
+    m_pool.addUnchecked(*entry, ws.m_ancestors, validForFeeEstimation);
 
     // trim mempool and check if tx was trimmed
     if (!bypass_limits) {
@@ -923,26 +998,24 @@ MempoolAcceptResult MemPoolAccept::AcceptSingleTransaction(const CTransactionRef
 
     if (!PreChecks(args, ws)) return MempoolAcceptResult::Failure(ws.m_state);
 
-    // Only compute the precomputed transaction data if we need to verify
-    // scripts (ie, other policy checks pass). We perform the inexpensive
-    // checks first and avoid hashing and signature verification unless those
-    // checks pass, to mitigate CPU exhaustion denial-of-service attacks.
-    PrecomputedTransactionData txdata;
+    if (m_rbf && !ReplacementChecks(ws)) return MempoolAcceptResult::Failure(ws.m_state);
 
-    if (!PolicyScriptChecks(args, ws, txdata)) return MempoolAcceptResult::Failure(ws.m_state);
+    // Perform the inexpensive checks first and avoid hashing and signature verification unless
+    // those checks pass, to mitigate CPU exhaustion denial-of-service attacks.
+    if (!PolicyScriptChecks(args, ws)) return MempoolAcceptResult::Failure(ws.m_state);
 
-    if (!ConsensusScriptChecks(args, ws, txdata)) return MempoolAcceptResult::Failure(ws.m_state);
+    if (!ConsensusScriptChecks(args, ws)) return MempoolAcceptResult::Failure(ws.m_state);
 
     // Tx was accepted, but not added
     if (args.m_test_accept) {
-        return MempoolAcceptResult::Success(std::move(ws.m_replaced_transactions), ws.m_base_fees);
+        return MempoolAcceptResult::Success(std::move(ws.m_replaced_transactions), ws.m_vsize, ws.m_base_fees);
     }
 
     if (!Finalize(args, ws)) return MempoolAcceptResult::Failure(ws.m_state);
 
     GetMainSignals().TransactionAddedToMempool(ptx, m_pool.GetAndIncrementSequence());
 
-    return MempoolAcceptResult::Success(std::move(ws.m_replaced_transactions), ws.m_base_fees);
+    return MempoolAcceptResult::Success(std::move(ws.m_replaced_transactions), ws.m_vsize, ws.m_base_fees);
 }
 
 PackageMempoolAcceptResult MemPoolAccept::AcceptMultipleTransactions(const std::vector<CTransactionRef>& txns, ATMPArgs& args)
@@ -981,18 +1054,12 @@ PackageMempoolAcceptResult MemPoolAccept::AcceptMultipleTransactions(const std::
     // because it's unnecessary. Also, CPFP carve out can increase the limit for individual
     // transactions, but this exemption is not extended to packages in CheckPackageLimits().
     std::string err_string;
-    if (txns.size() > 1 &&
-        !m_pool.CheckPackageLimits(txns, m_limit_ancestors, m_limit_ancestor_size, m_limit_descendants,
-                                   m_limit_descendant_size, err_string)) {
-        // All transactions must have individually passed mempool ancestor and descendant limits
-        // inside of PreChecks(), so this is separate from an individual transaction error.
-        package_state.Invalid(PackageValidationResult::PCKG_POLICY, "package-mempool-limits", err_string);
+    if (txns.size() > 1 && !PackageMempoolChecks(txns, package_state)) {
         return PackageMempoolAcceptResult(package_state, std::move(results));
     }
 
     for (Workspace& ws : workspaces) {
-        PrecomputedTransactionData txdata;
-        if (!PolicyScriptChecks(args, ws, txdata)) {
+        if (!PolicyScriptChecks(args, ws)) {
             // Exit early to avoid doing pointless work. Update the failed tx result; the rest are unfinished.
             package_state.Invalid(PackageValidationResult::PCKG_TX, "transaction failed");
             results.emplace(ws.m_ptx->GetWitnessHash(), MempoolAcceptResult::Failure(ws.m_state));
@@ -1002,7 +1069,8 @@ PackageMempoolAcceptResult MemPoolAccept::AcceptMultipleTransactions(const std::
             // When test_accept=true, transactions that pass PolicyScriptChecks are valid because there are
             // no further mempool checks (passing PolicyScriptChecks implies passing ConsensusScriptChecks).
             results.emplace(ws.m_ptx->GetWitnessHash(),
-                            MempoolAcceptResult::Success(std::move(ws.m_replaced_transactions), ws.m_base_fees));
+                            MempoolAcceptResult::Success(std::move(ws.m_replaced_transactions),
+                                                         ws.m_vsize, ws.m_base_fees));
         }
     }
 
@@ -1019,9 +1087,7 @@ static MempoolAcceptResult AcceptToMemoryPoolWithTime(const CChainParams& chainp
                                                       EXCLUSIVE_LOCKS_REQUIRED(cs_main)
 {
     std::vector<COutPoint> coins_to_uncache;
-    MemPoolAccept::ATMPArgs args { chainparams, nAcceptTime, bypass_limits, coins_to_uncache,
-                                   test_accept, /* m_allow_bip125_replacement */ true };
-
+    auto args = MemPoolAccept::ATMPArgs::SingleAccept(chainparams, nAcceptTime, bypass_limits, coins_to_uncache, test_accept);
     const MempoolAcceptResult result = MemPoolAccept(pool, active_chainstate).AcceptSingleTransaction(tx, args);
     if (result.m_result_type != MempoolAcceptResult::ResultType::VALID) {
         // Remove coins that were not present in the coins cache before calling
@@ -1054,8 +1120,7 @@ PackageMempoolAcceptResult ProcessNewPackage(CChainState& active_chainstate, CTx
 
     std::vector<COutPoint> coins_to_uncache;
     const CChainParams& chainparams = Params();
-    MemPoolAccept::ATMPArgs args { chainparams, GetTime(), /* bypass_limits */ false, coins_to_uncache,
-                                   test_accept, /* m_allow_bip125_replacement */ false };
+    auto args = MemPoolAccept::ATMPArgs::PackageTestAccept(chainparams, GetTime(), coins_to_uncache);
     const PackageMempoolAcceptResult result = MemPoolAccept(pool, active_chainstate).AcceptMultipleTransactions(package, args);
 
     // Uncache coins pertaining to transactions that were not submitted to the mempool.
diff --git a/src/validation.h b/src/validation.h
index 4da8ec8d24..256981224a 100644
--- a/src/validation.h
+++ b/src/validation.h
@@ -158,14 +158,16 @@ struct MempoolAcceptResult {
     // The following fields are only present when m_result_type = ResultType::VALID
     /** Mempool transactions replaced by the tx per BIP 125 rules. */
     const std::optional<std::list<CTransactionRef>> m_replaced_transactions;
+    /** Virtual size as used by the mempool, calculated using serialized size and sigops. */
+    const std::optional<int64_t> m_vsize;
     /** Raw base fees in satoshis. */
     const std::optional<CAmount> m_base_fees;
     static MempoolAcceptResult Failure(TxValidationState state) {
         return MempoolAcceptResult(state);
     }
 
-    static MempoolAcceptResult Success(std::list<CTransactionRef>&& replaced_txns, CAmount fees) {
-        return MempoolAcceptResult(std::move(replaced_txns), fees);
+    static MempoolAcceptResult Success(std::list<CTransactionRef>&& replaced_txns, int64_t vsize, CAmount fees) {
+        return MempoolAcceptResult(std::move(replaced_txns), vsize, fees);
     }
 
 // Private constructors. Use static methods MempoolAcceptResult::Success, etc. to construct.
@@ -177,9 +179,9 @@ private:
         }
 
     /** Constructor for success case */
-    explicit MempoolAcceptResult(std::list<CTransactionRef>&& replaced_txns, CAmount fees)
+    explicit MempoolAcceptResult(std::list<CTransactionRef>&& replaced_txns, int64_t vsize, CAmount fees)
         : m_result_type(ResultType::VALID),
-        m_replaced_transactions(std::move(replaced_txns)), m_base_fees(fees) {}
+        m_replaced_transactions(std::move(replaced_txns)), m_vsize{vsize}, m_base_fees(fees) {}
 };
 
 /**