diff --git a/ci/lint/04_install.sh b/ci/lint/04_install.sh
index 80d0df4a78..fae424051d 100755
--- a/ci/lint/04_install.sh
+++ b/ci/lint/04_install.sh
@@ -6,6 +6,10 @@
 
 export LC_ALL=C
 
+travis_retry sudo apt update && sudo apt install -y clang-format-9
+sudo update-alternatives --install /usr/bin/clang-format      clang-format      $(which clang-format-9     ) 100
+sudo update-alternatives --install /usr/bin/clang-format-diff clang-format-diff $(which clang-format-diff-9) 100
+
 travis_retry pip3 install codespell==1.17.1
 travis_retry pip3 install flake8==3.8.3
 travis_retry pip3 install yq
diff --git a/src/Makefile.am b/src/Makefile.am
index 7e1eab0249..3565eaacb2 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -114,10 +114,10 @@ BITCOIN_CORE_H = \
   bech32.h \
   blech32.h \
   blind.h \
-  bloom.h \
   blockencodings.h \
   blockfilter.h \
   block_proof.h \
+  bloom.h \
   chain.h \
   chainparams.h \
   chainparamsbase.h \
@@ -139,6 +139,7 @@ BITCOIN_CORE_H = \
   core_io.h \
   core_memusage.h \
   cuckoocache.h \
+  dbwrapper.h \
   dynafed.h \
   flatfile.h \
   fs.h \
@@ -156,7 +157,6 @@ BITCOIN_CORE_H = \
   issuance.h \
   key.h \
   key_io.h \
-  dbwrapper.h \
   limitedmap.h \
   logging.h \
   logging/timer.h \
@@ -176,6 +176,7 @@ BITCOIN_CORE_H = \
   node/context.h \
   node/psbt.h \
   node/transaction.h \
+  node/ui_interface.h \
   node/utxo_snapshot.h \
   noui.h \
   optional.h \
@@ -218,13 +219,12 @@ BITCOIN_CORE_H = \
   support/events.h \
   support/lockedpool.h \
   sync.h \
-  threadsafety.h \
   threadinterrupt.h \
+  threadsafety.h \
   timedata.h \
   torcontrol.h \
   txdb.h \
   txmempool.h \
-  ui_interface.h \
   undo.h \
   util/asmap.h \
   util/bip32.h \
@@ -233,8 +233,6 @@ BITCOIN_CORE_H = \
   util/error.h \
   util/fees.h \
   util/golombrice.h \
-  util/spanparsing.h \
-  util/system.h \
   util/macros.h \
   util/memory.h \
   util/message.h \
@@ -242,19 +240,22 @@ BITCOIN_CORE_H = \
   util/rbf.h \
   util/ref.h \
   util/settings.h \
+  util/spanparsing.h \
   util/string.h \
+  util/system.h \
   util/threadnames.h \
   util/time.h \
   util/translation.h \
+  util/ui_change_type.h \
   util/url.h \
   util/vector.h \
   validation.h \
   validationinterface.h \
   versionbits.h \
   versionbitsinfo.h \
-  walletinitinterface.h \
   wallet/bdb.h \
   wallet/coincontrol.h \
+  wallet/coinselection.h \
   wallet/context.h \
   wallet/crypter.h \
   wallet/db.h \
@@ -269,7 +270,7 @@ BITCOIN_CORE_H = \
   wallet/walletdb.h \
   wallet/wallettool.h \
   wallet/walletutil.h \
-  wallet/coinselection.h \
+  walletinitinterface.h \
   warnings.h \
   zmq/zmqabstractnotifier.h \
   zmq/zmqconfig.h\
@@ -301,16 +302,16 @@ libbitcoin_server_a_SOURCES = \
   chain.cpp \
   confidential_validation.cpp \
   consensus/tx_verify.cpp \
+  dbwrapper.cpp \
   flatfile.cpp \
   httprpc.cpp \
   httpserver.cpp \
   index/base.cpp \
   index/blockfilterindex.cpp \
   index/txindex.cpp \
+  init.cpp \
   interfaces/chain.cpp \
   interfaces/node.cpp \
-  init.cpp \
-  dbwrapper.cpp \
   mainchainrpc.cpp \
   miner.cpp \
   net.cpp \
@@ -320,6 +321,7 @@ libbitcoin_server_a_SOURCES = \
   node/context.cpp \
   node/psbt.cpp \
   node/transaction.cpp \
+  node/ui_interface.cpp \
   noui.cpp \
   pegins.cpp \
   policy/fees.cpp \
@@ -339,7 +341,6 @@ libbitcoin_server_a_SOURCES = \
   torcontrol.cpp \
   txdb.cpp \
   txmempool.cpp \
-  ui_interface.cpp \
   validation.cpp \
   validationinterface.cpp \
   versionbits.cpp \
diff --git a/src/banman.cpp b/src/banman.cpp
index 9cc584f0e4..422904bb33 100644
--- a/src/banman.cpp
+++ b/src/banman.cpp
@@ -6,7 +6,7 @@
 #include <banman.h>
 
 #include <netaddress.h>
-#include <ui_interface.h>
+#include <node/ui_interface.h>
 #include <util/system.h>
 #include <util/time.h>
 #include <util/translation.h>
diff --git a/src/bitcoind.cpp b/src/bitcoind.cpp
index 223df54c18..b80b6f384c 100644
--- a/src/bitcoind.cpp
+++ b/src/bitcoind.cpp
@@ -13,9 +13,9 @@
 #include <init.h>
 #include <interfaces/chain.h>
 #include <node/context.h>
+#include <node/ui_interface.h>
 #include <noui.h>
 #include <shutdown.h>
-#include <ui_interface.h>
 #include <util/ref.h>
 #include <util/strencodings.h>
 #include <util/system.h>
diff --git a/src/httpserver.cpp b/src/httpserver.cpp
index f1562c23f4..897e436650 100644
--- a/src/httpserver.cpp
+++ b/src/httpserver.cpp
@@ -7,10 +7,10 @@
 #include <chainparamsbase.h>
 #include <compat.h>
 #include <netbase.h>
+#include <node/ui_interface.h>
 #include <rpc/protocol.h> // For HTTP status codes
 #include <shutdown.h>
 #include <sync.h>
-#include <ui_interface.h>
 #include <util/strencodings.h>
 #include <util/system.h>
 #include <util/threadnames.h>
diff --git a/src/index/base.cpp b/src/index/base.cpp
index a93b67395d..f587205a28 100644
--- a/src/index/base.cpp
+++ b/src/index/base.cpp
@@ -4,9 +4,9 @@
 
 #include <chainparams.h>
 #include <index/base.h>
+#include <node/ui_interface.h>
 #include <shutdown.h>
 #include <tinyformat.h>
-#include <ui_interface.h>
 #include <util/system.h>
 #include <util/translation.h>
 #include <validation.h>
diff --git a/src/index/txindex.cpp b/src/index/txindex.cpp
index 2ae773bd3c..11ca5b8e13 100644
--- a/src/index/txindex.cpp
+++ b/src/index/txindex.cpp
@@ -3,8 +3,8 @@
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
 #include <index/txindex.h>
+#include <node/ui_interface.h>
 #include <shutdown.h>
-#include <ui_interface.h>
 #include <util/system.h>
 #include <util/translation.h>
 #include <validation.h>
diff --git a/src/init.cpp b/src/init.cpp
index c489b5e5c5..d34dc9294d 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -32,6 +32,7 @@
 #include <net_processing.h>
 #include <netbase.h>
 #include <node/context.h>
+#include <node/ui_interface.h>
 #include <policy/feerate.h>
 #include <policy/fees.h>
 #include <policy/policy.h>
@@ -49,7 +50,6 @@
 #include <torcontrol.h>
 #include <txdb.h>
 #include <txmempool.h>
-#include <ui_interface.h>
 #include <util/asmap.h>
 #include <util/moneystr.h>
 #include <util/strencodings.h>
diff --git a/src/interfaces/chain.cpp b/src/interfaces/chain.cpp
index fd07092a81..00498207be 100644
--- a/src/interfaces/chain.cpp
+++ b/src/interfaces/chain.cpp
@@ -13,6 +13,7 @@
 #include <node/coin.h>
 #include <node/context.h>
 #include <node/transaction.h>
+#include <node/ui_interface.h>
 #include <policy/fees.h>
 #include <policy/policy.h>
 #include <policy/rbf.h>
@@ -25,7 +26,6 @@
 #include <sync.h>
 #include <timedata.h>
 #include <txmempool.h>
-#include <ui_interface.h>
 #include <uint256.h>
 #include <univalue.h>
 #include <util/system.h>
diff --git a/src/interfaces/node.cpp b/src/interfaces/node.cpp
index 0664c6a826..db5f2ddb8c 100644
--- a/src/interfaces/node.cpp
+++ b/src/interfaces/node.cpp
@@ -17,6 +17,7 @@
 #include <netaddress.h>
 #include <netbase.h>
 #include <node/context.h>
+#include <node/ui_interface.h>
 #include <policy/feerate.h>
 #include <policy/fees.h>
 #include <policy/settings.h>
@@ -26,7 +27,6 @@
 #include <support/allocators/secure.h>
 #include <sync.h>
 #include <txmempool.h>
-#include <ui_interface.h>
 #include <util/ref.h>
 #include <util/system.h>
 #include <util/translation.h>
diff --git a/src/interfaces/wallet.cpp b/src/interfaces/wallet.cpp
index cff64f2f0f..51a9db6fe9 100644
--- a/src/interfaces/wallet.cpp
+++ b/src/interfaces/wallet.cpp
@@ -13,11 +13,11 @@
 #include <script/standard.h>
 #include <support/allocators/secure.h>
 #include <sync.h>
-#include <ui_interface.h>
 #include <uint256.h>
 #include <util/check.h>
 #include <util/ref.h>
 #include <util/system.h>
+#include <util/ui_change_type.h>
 #include <wallet/context.h>
 #include <wallet/feebumper.h>
 #include <wallet/fees.h>
diff --git a/src/interfaces/wallet.h b/src/interfaces/wallet.h
index 92b1faff4a..13102acebe 100644
--- a/src/interfaces/wallet.h
+++ b/src/interfaces/wallet.h
@@ -10,8 +10,8 @@
 #include <pubkey.h>                    // For CKeyID and CScriptID (definitions needed in CTxDestination instantiation)
 #include <script/standard.h>           // For CTxDestination
 #include <support/allocators/secure.h> // For SecureString
-#include <ui_interface.h>              // For ChangeType
 #include <util/message.h>
+#include <util/ui_change_type.h>
 
 #include <functional>
 #include <map>
diff --git a/src/net.cpp b/src/net.cpp
index 371fbeed59..281232d801 100644
--- a/src/net.cpp
+++ b/src/net.cpp
@@ -14,12 +14,12 @@
 #include <clientversion.h>
 #include <consensus/consensus.h>
 #include <crypto/sha256.h>
-#include <netbase.h>
 #include <net_permissions.h>
+#include <netbase.h>
+#include <node/ui_interface.h>
 #include <protocol.h>
 #include <random.h>
 #include <scheduler.h>
-#include <ui_interface.h>
 #include <util/strencodings.h>
 #include <util/translation.h>
 
diff --git a/src/ui_interface.cpp b/src/node/ui_interface.cpp
similarity index 99%
rename from src/ui_interface.cpp
rename to src/node/ui_interface.cpp
index 15795bd67f..9ccd8e27e2 100644
--- a/src/ui_interface.cpp
+++ b/src/node/ui_interface.cpp
@@ -2,7 +2,7 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
-#include <ui_interface.h>
+#include <node/ui_interface.h>
 
 #include <util/translation.h>
 
diff --git a/src/ui_interface.h b/src/node/ui_interface.h
similarity index 94%
rename from src/ui_interface.h
rename to src/node/ui_interface.h
index b7895e373f..d574ab879f 100644
--- a/src/ui_interface.h
+++ b/src/node/ui_interface.h
@@ -3,8 +3,8 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
-#ifndef BITCOIN_UI_INTERFACE_H
-#define BITCOIN_UI_INTERFACE_H
+#ifndef BITCOIN_NODE_UI_INTERFACE_H
+#define BITCOIN_NODE_UI_INTERFACE_H
 
 #include <functional>
 #include <memory>
@@ -20,14 +20,6 @@ class connection;
 }
 } // namespace boost
 
-/** General change type (added, updated, removed). */
-enum ChangeType
-{
-    CT_NEW,
-    CT_UPDATED,
-    CT_DELETED
-};
-
 /** Signals for UI communication. */
 class CClientUIInterface
 {
@@ -122,8 +114,8 @@ void InitWarning(const bilingual_str& str);
 
 /** Show error message **/
 bool InitError(const bilingual_str& str);
-inline bool AbortError(const bilingual_str& str) { return InitError(str); }
+constexpr auto AbortError = InitError;
 
 extern CClientUIInterface uiInterface;
 
-#endif // BITCOIN_UI_INTERFACE_H
+#endif // BITCOIN_NODE_UI_INTERFACE_H
diff --git a/src/noui.cpp b/src/noui.cpp
index 821d10e3bc..3c82512fac 100644
--- a/src/noui.cpp
+++ b/src/noui.cpp
@@ -6,7 +6,7 @@
 #include <noui.h>
 
 #include <logging.h>
-#include <ui_interface.h>
+#include <node/ui_interface.h>
 #include <util/translation.h>
 
 #include <string>
diff --git a/src/qt/bitcoin.cpp b/src/qt/bitcoin.cpp
index cce18f6cad..b9354b45dd 100644
--- a/src/qt/bitcoin.cpp
+++ b/src/qt/bitcoin.cpp
@@ -29,11 +29,10 @@
 #include <interfaces/handler.h>
 #include <interfaces/node.h>
 #include <noui.h>
-#include <ui_interface.h>
 #include <uint256.h>
 #include <util/system.h>
-#include <util/translation.h>
 #include <util/threadnames.h>
+#include <util/translation.h>
 #include <validation.h>
 
 #include <memory>
diff --git a/src/qt/bitcoingui.cpp b/src/qt/bitcoingui.cpp
index 344ec15c98..ebfe890275 100644
--- a/src/qt/bitcoingui.cpp
+++ b/src/qt/bitcoingui.cpp
@@ -34,7 +34,7 @@
 #include <chainparams.h>
 #include <interfaces/handler.h>
 #include <interfaces/node.h>
-#include <ui_interface.h>
+#include <node/ui_interface.h>
 #include <util/system.h>
 #include <util/translation.h>
 #include <validation.h>
diff --git a/src/qt/paymentserver.cpp b/src/qt/paymentserver.cpp
index 98d130a6ce..79a098bca6 100644
--- a/src/qt/paymentserver.cpp
+++ b/src/qt/paymentserver.cpp
@@ -14,9 +14,9 @@
 
 #include <chainparams.h>
 #include <interfaces/node.h>
-#include <policy/policy.h>
 #include <key_io.h>
-#include <ui_interface.h>
+#include <node/ui_interface.h>
+#include <policy/policy.h>
 #include <util/system.h>
 #include <wallet/wallet.h>
 
diff --git a/src/qt/sendcoinsdialog.cpp b/src/qt/sendcoinsdialog.cpp
index 7372455ee9..50d8431cc0 100644
--- a/src/qt/sendcoinsdialog.cpp
+++ b/src/qt/sendcoinsdialog.cpp
@@ -21,10 +21,10 @@
 #include <chainparams.h>
 #include <interfaces/node.h>
 #include <key_io.h>
+#include <node/ui_interface.h>
 #include <policy/fees.h>
 #include <policy/policy.h>
 #include <txmempool.h>
-#include <ui_interface.h>
 #include <wallet/coincontrol.h>
 #include <wallet/fees.h>
 #include <wallet/wallet.h>
diff --git a/src/qt/splashscreen.cpp b/src/qt/splashscreen.cpp
index 96052ef459..df52c64e40 100644
--- a/src/qt/splashscreen.cpp
+++ b/src/qt/splashscreen.cpp
@@ -14,7 +14,6 @@
 #include <interfaces/wallet.h>
 #include <qt/guiutil.h>
 #include <qt/networkstyle.h>
-#include <ui_interface.h>
 #include <util/system.h>
 #include <util/translation.h>
 
diff --git a/src/qt/transactionview.cpp b/src/qt/transactionview.cpp
index b0314e010e..d3008ade90 100644
--- a/src/qt/transactionview.cpp
+++ b/src/qt/transactionview.cpp
@@ -17,7 +17,7 @@
 #include <qt/transactiontablemodel.h>
 #include <qt/walletmodel.h>
 
-#include <ui_interface.h>
+#include <node/ui_interface.h>
 
 #include <QApplication>
 #include <QComboBox>
diff --git a/src/qt/walletmodel.cpp b/src/qt/walletmodel.cpp
index 6fde0a886e..eb7b3f38b9 100644
--- a/src/qt/walletmodel.cpp
+++ b/src/qt/walletmodel.cpp
@@ -20,9 +20,9 @@
 #include <interfaces/handler.h>
 #include <interfaces/node.h>
 #include <key_io.h>
+#include <node/ui_interface.h>
 #include <policy/policy.h>
 #include <psbt.h>
-#include <ui_interface.h>
 #include <util/system.h> // for GetBoolArg
 #include <util/translation.h>
 #include <wallet/coincontrol.h>
diff --git a/src/qt/walletview.cpp b/src/qt/walletview.cpp
index 54197769dc..860d775d2e 100644
--- a/src/qt/walletview.cpp
+++ b/src/qt/walletview.cpp
@@ -20,8 +20,8 @@
 #include <qt/walletmodel.h>
 
 #include <interfaces/node.h>
+#include <node/ui_interface.h>
 #include <psbt.h>
-#include <ui_interface.h>
 #include <util/strencodings.h>
 
 #include <QAction>
diff --git a/src/timedata.cpp b/src/timedata.cpp
index 16dac24a48..6b3a79017b 100644
--- a/src/timedata.cpp
+++ b/src/timedata.cpp
@@ -9,8 +9,8 @@
 #include <timedata.h>
 
 #include <netaddress.h>
+#include <node/ui_interface.h>
 #include <sync.h>
-#include <ui_interface.h>
 #include <util/system.h>
 #include <util/translation.h>
 #include <warnings.h>
diff --git a/src/txdb.cpp b/src/txdb.cpp
index 4149331e61..94a76edbc2 100644
--- a/src/txdb.cpp
+++ b/src/txdb.cpp
@@ -5,10 +5,10 @@
 
 #include <txdb.h>
 
+#include <node/ui_interface.h>
 #include <pow.h>
 #include <random.h>
 #include <shutdown.h>
-#include <ui_interface.h>
 #include <uint256.h>
 #include <util/system.h>
 #include <util/translation.h>
diff --git a/src/util/ui_change_type.h b/src/util/ui_change_type.h
new file mode 100644
index 0000000000..1db761a18d
--- /dev/null
+++ b/src/util/ui_change_type.h
@@ -0,0 +1,15 @@
+// Copyright (c) 2012-2020 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#ifndef BITCOIN_UTIL_UI_CHANGE_TYPE_H
+#define BITCOIN_UTIL_UI_CHANGE_TYPE_H
+
+/** General change type (added, updated, removed). */
+enum ChangeType {
+    CT_NEW,
+    CT_UPDATED,
+    CT_DELETED
+};
+
+#endif // BITCOIN_UTIL_UI_CHANGE_TYPE_H
diff --git a/src/validation.cpp b/src/validation.cpp
index c069cfa6ca..7be1266548 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -21,6 +21,7 @@
 #include <logging.h>
 #include <logging/timer.h>
 #include <mainchainrpc.h>
+#include <node/ui_interface.h>
 #include <optional.h>
 #include <pegins.h>
 #include <policy/fees.h>
@@ -38,7 +39,6 @@
 #include <tinyformat.h>
 #include <txdb.h>
 #include <txmempool.h>
-#include <ui_interface.h>
 #include <uint256.h>
 #include <undo.h>
 #include <util/moneystr.h>
diff --git a/src/wallet/init.cpp b/src/wallet/init.cpp
index 3885eb6185..f173b5e62b 100644
--- a/src/wallet/init.cpp
+++ b/src/wallet/init.cpp
@@ -7,8 +7,8 @@
 #include <interfaces/chain.h>
 #include <net.h>
 #include <node/context.h>
+#include <node/ui_interface.h>
 #include <outputtype.h>
-#include <ui_interface.h>
 #include <util/moneystr.h>
 #include <util/system.h>
 #include <util/translation.h>
diff --git a/src/wallet/wallet.h b/src/wallet/wallet.h
index 4741e3c1ba..176807c25b 100644
--- a/src/wallet/wallet.h
+++ b/src/wallet/wallet.h
@@ -14,11 +14,11 @@
 #include <policy/feerate.h>
 #include <psbt.h>
 #include <tinyformat.h>
-#include <ui_interface.h>
 #include <util/message.h>
 #include <util/strencodings.h>
 #include <util/string.h>
 #include <util/system.h>
+#include <util/ui_change_type.h>
 #include <validationinterface.h>
 #include <wallet/coinselection.h>
 #include <wallet/crypter.h>