diff --git a/src/content/api/_endpoints/payment-requests-pay.js b/src/content/api/_endpoints/payment-requests-pay.js
index 738371c8e..a48409fa2 100644
--- a/src/content/api/_endpoints/payment-requests-pay.js
+++ b/src/content/api/_endpoints/payment-requests-pay.js
@@ -7,6 +7,7 @@ export default {
       'Content-Type': 'application/json',
     },
     payload: {
+      idempotencyKey: 'b62-11ec-9072-3e22fb52e878',
       assetType: 'centrapay.nzd.main',
       assetId: 'WRhAxxWpTKb5U7pXyxQjjY',
       amount: '200',
@@ -20,6 +21,7 @@ export default {
       currency: 'NZD',
       amount: '1000'
     },
+    idempotencyKey: '8b62-11ec-9072-3e22fb52e878',
     assetType: 'centrapay.nzd.main',
     paymentRequestId: 'MhocUmpxxmgdHjr7DgKoKw',
     shortCode: 'CP-C7F-ZS5-015',
diff --git a/src/content/api/payment-requests.mdoc b/src/content/api/payment-requests.mdoc
index 3f4ec4059..b7c7b9e12 100644
--- a/src/content/api/payment-requests.mdoc
+++ b/src/content/api/payment-requests.mdoc
@@ -615,12 +615,15 @@ Payment Activities are created when a Payment Request has been `created`, `paid`
 %}
   ## Pay a Payment Request
 
-  To pay a Payment Request you must supply the name of the [Asset Type](/api/asset-types) and one of `assetId`, `transactionId` or `authorization`.
+  To pay a Payment Request you must supply the name of the [Asset Type](/api/asset-types) , `idempotencyKey` and one of `assetId`, `transactionId` or `authorization`.
   - Use `assetId` if the [Asset Type](/api/asset-types) is managed by Centrapay.
   - Use `transactionId` to verify an external transaction such as a Bitcoin payment.
   - Use `authorization` to authorize an external transaction.
 
   {% properties %}
+    {% property name="idempotencyKey" type="string" required=true %}
+      A unique identifier that prevents duplicate processing of the same request.
+    {% /property %}
     {% property name="assetType" type="string" required=true %}
       An [Asset Type](/api/asset-types) reference.
     {% /property %}