diff --git a/.changeset/swift-shirts-peel.md b/.changeset/swift-shirts-peel.md
new file mode 100644
index 00000000..18540912
--- /dev/null
+++ b/.changeset/swift-shirts-peel.md
@@ -0,0 +1,5 @@
+---
+'guard-service': major
+---
+
+change paymentTxId format in R4 from hex string to string
diff --git a/src/event/EventOrder.ts b/src/event/EventOrder.ts
index fc173256..579f0694 100644
--- a/src/event/EventOrder.ts
+++ b/src/event/EventOrder.ts
@@ -333,7 +333,7 @@ class EventOrder {
     guardsOrder.push({
       address: GuardsErgoConfigs.bridgeFeeRepoAddress,
       assets: assets,
-      extra: paymentTxId,
+      extra: Buffer.from(paymentTxId).toString(),
     });
 
     // add emission to order
@@ -454,7 +454,7 @@ class EventOrder {
         nativeToken: minimumErg,
         tokens: guardTokens,
       },
-      extra: paymentTxId,
+      extra: Buffer.from(paymentTxId).toString(),
     });
 
     // add emission to order