Cancel Payment Order (by Merchant Order ID)

Cancel an open payment order from your backend using your own merchant_order_id — the id you sent to /payment-flex/create. The platform resolves it to the gateway order internally, so you do not need to have stored the returned platform_order_id.

This is the same operation as /payment/cancel, but keyed by your order id instead of the gateway one. The main use case is clearing the pending-order 409 returned by /payment-flex/create: only one open FLEX order is allowed per customer account at a time, so a second create returns

{
  "success": false,
  "code": 409,
  "error": "you have a pending payment order. complete or cancel it first.",
  "data": { "pending_order_id": "THBP20260613123300zBuseUwN" }
}

Call /payment/cancel-by-merchant-order-id with the merchant_order_id of the stuck order to cancel it, then retry the create.

The customer can also cancel from the hosted payment page itself. This endpoint is the server-to-server equivalent for your backend.

URL : /payment/cancel-by-merchant-order-id

Method : POST

Request

{
   "merchant_id" : "[Merchant id]",
   "token" : "[Auth Token]",
   "time" : "[Time Stamp]",
   "merchant_order_id" : "[your merchant order id to cancel]"
}

Data example

{
  "merchant_id": "AA12345678",
  "token": "testtokentesttokentesttokentesttokentesttoken",
  "time": 1656272222,
  "merchant_order_id": "ORDER0123456789789445566"
}

When can an order be cancelled?

A cancel succeeds only when all of the following hold:

• The order belongs to your merchant account.
• The order was created within the last 24 hours (the internal resolution window).
• The order status is open (not yet paid, expired, or already cancelled).
• No payment slip has been uploaded for the order yet.

On a successful cancel the system also:

• releases the pending-order guard — so you can immediately create a new order for the same customer account,
• sends a CANCELLED payment callback to your notify_url (see Payment Callback).

⚠️ A cancel is not always final: in some cases the order may still be paid afterwards, in which case a subsequent PAID callback follows for the same platform_order_id — always treat PAID as authoritative.

Success Response

Code : 200 OK

{
    "success": 200,
    "data": {
        "platform_order_id": "THBP20260613123300zBuseUwN",
        "merchant_order_id": "ORDER0123456789789445566",
        "status": "cancelled"
    }
}

A retry of a cancel on an already-cancelled order also returns 200 (with "already_cancelled": true) — the call is idempotent.

Error Responses

Condition : Invalid merchant id, token, or signature

Code : 403

{ "error": { "code": 403, "message": "authentication failed" } }

Condition : Order not found — the merchant_order_id was not created via FLEX, is older than 24 hours, or is not owned by you.

Code : 500

{ "error": { "code": 500, "message": "merchant order id not found" } }

Condition : Order exists but cannot be cancelled — not open, a slip was already uploaded, or it is past the cancellable window.

Code : 409

{ "success": false, "code": 409, "error": "cannot cancel order" }