diff --git a/packages/polkadart/lib/extrinsic/extrinsic_payload.dart b/packages/polkadart/lib/extrinsic/extrinsic_payload.dart
index 4be01f1d..310f0bb2 100644
--- a/packages/polkadart/lib/extrinsic/extrinsic_payload.dart
+++ b/packages/polkadart/lib/extrinsic/extrinsic_payload.dart
@@ -30,7 +30,7 @@ class Extrinsic {
     this.assetId,
   });
 
-  toEncodedMap() {
+  toEncodedMap(dynamic registry) {
     return {
       'signer': signer,
       'method': method,
@@ -39,7 +39,7 @@ class Extrinsic {
           ? '00'
           : Era.codec.encodeMortal(blockNumber, eraPeriod),
       'nonce': encodeHex(CompactCodec.codec.encode(nonce)),
-      'assetId': assetId != null ? assetId!.toRadixString(16) : '',
+      'assetId': maybeAssetIdEncoded(registry),
       'tip': tip is int
           ? encodeHex(CompactCodec.codec.encode(tip))
           : encodeHex(CompactBigIntCodec.codec.encode(tip)),
@@ -68,15 +68,18 @@ class Extrinsic {
     final List<String> extras = <String>[];
 
     late final SignedExtensions signedExtensions;
-    if (assetId != null) {
+
+    if (_usesChargeAssetTxPayment(registry)) {
       signedExtensions = SignedExtensions.assetHubSignedExtensions;
     } else {
       signedExtensions = SignedExtensions.substrateSignedExtensions;
     }
 
     for (final signedExtensiontype in registry.getSignedExtensionTypes()) {
-      final payload =
-          signedExtensions.signedExtension(signedExtensiontype, toEncodedMap());
+      final payload = signedExtensions.signedExtension(
+        signedExtensiontype,
+        toEncodedMap(registry),
+      );
 
       if (payload.isNotEmpty) {
         extras.add(payload);
@@ -108,4 +111,16 @@ class Extrinsic {
       dynamic registry, SignatureType signatureType, keyring.KeyPair keyPair) {
     return keyPair.sign(encode(registry, signatureType));
   }
+
+  bool _usesChargeAssetTxPayment(dynamic registry) {
+    return registry.getSignedExtensionTypes().contains('ChargeAssetTxPayment');
+  }
+
+  String maybeAssetIdEncoded(dynamic registry) {
+    if (_usesChargeAssetTxPayment(registry)) {
+      return assetId != null ? assetId!.toRadixString(16) : '00';
+    } else {
+      return '';
+    }
+  }
 }
diff --git a/packages/polkadart/lib/extrinsic/signing_payload.dart b/packages/polkadart/lib/extrinsic/signing_payload.dart
index 342b6760..3859bb2c 100644
--- a/packages/polkadart/lib/extrinsic/signing_payload.dart
+++ b/packages/polkadart/lib/extrinsic/signing_payload.dart
@@ -30,7 +30,7 @@ class SigningPayload {
     this.assetId,
   });
 
-  toEncodedMap() {
+  toEncodedMap(dynamic registry) {
     return {
       'method': method,
       'specVersion': encodeHex(U32Codec.codec.encode(specVersion)),
@@ -42,7 +42,7 @@ class SigningPayload {
           ? '00'
           : Era.codec.encodeMortal(blockNumber, eraPeriod),
       'nonce': encodeHex(CompactCodec.codec.encode(nonce)),
-      'assetId': assetId != null ? assetId!.toRadixString(16) : '',
+      'assetId': maybeAssetIdEncoded(registry),
       'tip': tip is int
           ? encodeHex(CompactCodec.codec.encode(tip))
           : encodeHex(CompactBigIntCodec.codec.encode(tip)),
@@ -58,7 +58,7 @@ class SigningPayload {
     final List<String> additionalExtras = <String>[];
 
     late final SignedExtensions signedExtensions;
-    if (assetId != null) {
+    if (_usesChargeAssetTxPayment(registry)) {
       signedExtensions = SignedExtensions.assetHubSignedExtensions;
     } else {
       signedExtensions = SignedExtensions.substrateSignedExtensions;
@@ -66,7 +66,7 @@ class SigningPayload {
 
     registry.getSignedExtensionTypes().forEach((extension) {
       final payload =
-          signedExtensions.signedExtension(extension, toEncodedMap());
+          signedExtensions.signedExtension(extension, toEncodedMap(registry));
 
       if (payload.isNotEmpty) {
         extras.add(payload);
@@ -74,8 +74,10 @@ class SigningPayload {
     });
 
     registry.getSignedExtensionExtra().forEach((extension) {
-      final payload =
-          signedExtensions.additionalSignedExtension(extension, toEncodedMap());
+      final payload = signedExtensions.additionalSignedExtension(
+        extension,
+        toEncodedMap(registry),
+      );
 
       if (payload.isNotEmpty) {
         additionalExtras.add(payload);
@@ -88,4 +90,16 @@ class SigningPayload {
 
     return Uint8List.fromList(hex.decode(payload));
   }
+
+  bool _usesChargeAssetTxPayment(dynamic registry) {
+    return registry.getSignedExtensionTypes().contains('ChargeAssetTxPayment');
+  }
+
+  String maybeAssetIdEncoded(dynamic registry) {
+    if (_usesChargeAssetTxPayment(registry)) {
+      return assetId != null ? assetId!.toRadixString(16) : '00';
+    } else {
+      return '';
+    }
+  }
 }