diff --git a/src/addrman.cpp b/src/addrman.cpp
--- a/src/addrman.cpp
+++ b/src/addrman.cpp
@@ -725,7 +725,7 @@
         return CAddrInfo();
     }
 
-    CAddrInfo &newInfo = id_new_it->second;
+    const CAddrInfo &newInfo = id_new_it->second;
 
     // which tried bucket to move the entry to
     int tried_bucket = newInfo.GetTriedBucket(nKey, m_asmap);
diff --git a/src/logging.h b/src/logging.h
--- a/src/logging.h
+++ b/src/logging.h
@@ -150,9 +150,9 @@
     bool WillLogCategory(LogFlags category) const;
 
     /** Returns a vector of the log categories */
-    std::vector<LogCategory> LogCategoriesList();
+    std::vector<LogCategory> LogCategoriesList() const;
     /** Returns a string with the log categories */
-    std::string LogCategoriesString() {
+    std::string LogCategoriesString() const {
         return Join(LogCategoriesList(), ", ",
                     [&](const LogCategory &i) { return i.category; });
     };
diff --git a/src/logging.cpp b/src/logging.cpp
--- a/src/logging.cpp
+++ b/src/logging.cpp
@@ -142,7 +142,7 @@
     return false;
 }
 
-std::vector<LogCategory> BCLog::Logger::LogCategoriesList() {
+std::vector<LogCategory> BCLog::Logger::LogCategoriesList() const {
     std::vector<LogCategory> ret;
     for (const CLogCategoryDesc &category_desc : LogCategories) {
         // Omit the special cases.
diff --git a/src/miner.h b/src/miner.h
--- a/src/miner.h
+++ b/src/miner.h
@@ -203,7 +203,7 @@
      * succeed, and they're here only as an extra check in case of suboptimal
      * node configuration.
      */
-    bool TestPackageTransactions(const CTxMemPool::setEntries &package);
+    bool TestPackageTransactions(const CTxMemPool::setEntries &package) const;
     /**
      * Return true if given transaction from mapTx has already been evaluated,
      * or if the transaction's cached data in mapTx is incorrect.
diff --git a/src/miner.cpp b/src/miner.cpp
--- a/src/miner.cpp
+++ b/src/miner.cpp
@@ -273,7 +273,7 @@
  * - Serialized size (in case -blockmaxsize is in use)
  */
 bool BlockAssembler::TestPackageTransactions(
-    const CTxMemPool::setEntries &package) {
+    const CTxMemPool::setEntries &package) const {
     uint64_t nPotentialBlockSize = nBlockSize;
     for (CTxMemPool::txiter it : package) {
         TxValidationState state;
diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
--- a/src/rpc/blockchain.cpp
+++ b/src/rpc/blockchain.cpp
@@ -61,7 +61,7 @@
 }
 
 CTxMemPool &EnsureMemPool(const util::Ref &context) {
-    NodeContext &node = EnsureNodeContext(context);
+    const NodeContext &node = EnsureNodeContext(context);
     if (!node.mempool) {
         throw JSONRPCError(RPC_CLIENT_MEMPOOL_DISABLED,
                            "Mempool disabled or instance not found");
@@ -70,7 +70,7 @@
 }
 
 ChainstateManager &EnsureChainman(const util::Ref &context) {
-    NodeContext &node = EnsureNodeContext(context);
+    const NodeContext &node = EnsureNodeContext(context);
     if (!node.chainman) {
         throw JSONRPCError(RPC_INTERNAL_ERROR, "Node chainman not found");
     }
diff --git a/src/script/interpreter.cpp b/src/script/interpreter.cpp
--- a/src/script/interpreter.cpp
+++ b/src/script/interpreter.cpp
@@ -127,8 +127,8 @@
     uint32_t m_first_false_pos = NO_FALSE;
 
 public:
-    bool empty() { return m_stack_size == 0; }
-    bool all_true() { return m_first_false_pos == NO_FALSE; }
+    bool empty() const { return m_stack_size == 0; }
+    bool all_true() const { return m_first_false_pos == NO_FALSE; }
     void push_back(bool f) {
         if (m_first_false_pos == NO_FALSE && !f) {
             // The stack consists of all true values, and a false is added.
diff --git a/src/script/sign.cpp b/src/script/sign.cpp
--- a/src/script/sign.cpp
+++ b/src/script/sign.cpp
@@ -363,7 +363,7 @@
                    CMutableTransaction &txTo, unsigned int nIn,
                    SigHashType sigHashType) {
     assert(nIn < txTo.vin.size());
-    CTxIn &txin = txTo.vin[nIn];
+    const CTxIn &txin = txTo.vin[nIn];
     assert(txin.prevout.GetN() < txFrom.vout.size());
     const CTxOut &txout = txFrom.vout[txin.prevout.GetN()];
 
diff --git a/src/test/checkqueue_tests.cpp b/src/test/checkqueue_tests.cpp
--- a/src/test/checkqueue_tests.cpp
+++ b/src/test/checkqueue_tests.cpp
@@ -27,7 +27,7 @@
 static const int SCRIPT_CHECK_THREADS = 3;
 
 struct FakeCheck {
-    bool operator()() { return true; }
+    bool operator()() const { return true; }
     void swap(FakeCheck &x){};
 };
 
@@ -44,7 +44,7 @@
     bool fails;
     FailingCheck(bool _fails) : fails(_fails){};
     FailingCheck() : fails(true){};
-    bool operator()() { return !fails; }
+    bool operator()() const { return !fails; }
     void swap(FailingCheck &x) { std::swap(fails, x.fails); };
 };
 
@@ -65,7 +65,7 @@
 struct MemoryCheck {
     static std::atomic<size_t> fake_allocated_memory;
     bool b{false};
-    bool operator()() { return true; }
+    bool operator()() const { return true; }
     MemoryCheck(){};
     MemoryCheck(const MemoryCheck &x) {
         // We have to do this to make sure that destructor calls are paired
@@ -90,7 +90,7 @@
     // Freezing can't be the default initialized behavior given how the queue
     // swaps in default initialized Checks.
     bool should_freeze{false};
-    bool operator()() { return true; }
+    bool operator()() const { return true; }
     FrozenCleanupCheck() {}
     ~FrozenCleanupCheck() {
         if (should_freeze) {
diff --git a/src/test/util/setup_common.h b/src/test/util/setup_common.h
--- a/src/test/util/setup_common.h
+++ b/src/test/util/setup_common.h
@@ -164,8 +164,8 @@
     TestMemPoolEntryHelper()
         : nFee(), nTime(0), nHeight(1), spendsCoinbase(false), nSigOpCount(1) {}
 
-    CTxMemPoolEntry FromTx(const CMutableTransaction &tx);
-    CTxMemPoolEntry FromTx(const CTransactionRef &tx);
+    CTxMemPoolEntry FromTx(const CMutableTransaction &tx) const;
+    CTxMemPoolEntry FromTx(const CTransactionRef &tx) const;
 
     // Change the default value
     TestMemPoolEntryHelper &Fee(Amount _fee) {
diff --git a/src/test/util/setup_common.cpp b/src/test/util/setup_common.cpp
--- a/src/test/util/setup_common.cpp
+++ b/src/test/util/setup_common.cpp
@@ -292,11 +292,13 @@
 
 TestChain100Setup::~TestChain100Setup() {}
 
-CTxMemPoolEntry TestMemPoolEntryHelper::FromTx(const CMutableTransaction &tx) {
+CTxMemPoolEntry
+TestMemPoolEntryHelper::FromTx(const CMutableTransaction &tx) const {
     return FromTx(MakeTransactionRef(tx));
 }
 
-CTxMemPoolEntry TestMemPoolEntryHelper::FromTx(const CTransactionRef &tx) {
+CTxMemPoolEntry
+TestMemPoolEntryHelper::FromTx(const CTransactionRef &tx) const {
     return CTxMemPoolEntry(tx, nFee, nTime, nHeight, spendsCoinbase,
                            nSigOpCount, LockPoints());
 }
diff --git a/src/validation.h b/src/validation.h
--- a/src/validation.h
+++ b/src/validation.h
@@ -814,7 +814,7 @@
     //! @returns whether or not the CoinsViews object has been fully initialized
     //! and we can
     //!          safely flush this object to disk.
-    bool CanFlushToDisk() EXCLUSIVE_LOCKS_REQUIRED(cs_main) {
+    bool CanFlushToDisk() const EXCLUSIVE_LOCKS_REQUIRED(cs_main) {
         return m_coins_views && m_coins_views->m_cacheview;
     }
 
diff --git a/src/validation.cpp b/src/validation.cpp
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -494,7 +494,7 @@
     LockPoints lp;
     m_view.SetBackend(m_viewmempool);
 
-    CCoinsViewCache &coins_cache = ::ChainstateActive().CoinsTip();
+    const CCoinsViewCache &coins_cache = ::ChainstateActive().CoinsTip();
     // Do all inputs exist?
     for (const CTxIn &txin : tx.vin) {
         if (!coins_cache.HaveCoinInCache(txin.prevout)) {
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -1108,7 +1108,7 @@
 
     OutputType
     TransactionChangeType(const std::optional<OutputType> &change_type,
-                          const std::vector<CRecipient> &vecSend);
+                          const std::vector<CRecipient> &vecSend) const;
 
     /**
      * Insert additional inputs into the transaction by calling
diff --git a/src/wallet/wallet.cpp b/src/wallet/wallet.cpp
--- a/src/wallet/wallet.cpp
+++ b/src/wallet/wallet.cpp
@@ -694,7 +694,7 @@
 void CWallet::AddToSpends(const TxId &wtxid) {
     auto it = mapWallet.find(wtxid);
     assert(it != mapWallet.end());
-    CWalletTx &thisTx = it->second;
+    const CWalletTx &thisTx = it->second;
     // Coinbases don't spend anything!
     if (thisTx.IsCoinBase()) {
         return;
@@ -1176,7 +1176,7 @@
     // Can't mark abandoned if confirmed or in mempool
     auto it = mapWallet.find(txid);
     assert(it != mapWallet.end());
-    CWalletTx &origtx = it->second;
+    const CWalletTx &origtx = it->second;
     if (origtx.GetDepthInMainChain() != 0 || origtx.InMempool()) {
         return false;
     }
@@ -3095,7 +3095,7 @@
 
 OutputType
 CWallet::TransactionChangeType(const std::optional<OutputType> &change_type,
-                               const std::vector<CRecipient> &vecSend) {
+                               const std::vector<CRecipient> &vecSend) const {
     // If -changetype is specified, always use that change type.
     if (change_type) {
         return *change_type;