Cancel a Transaction

"Cancelling" a ToP transaction is actually two distinct SDK operations, depending on whether a result has already come back:

• Abort an in-flight transaction — the user backs out, or you need to stop waiting for a card tap, before any result has arrived.
• Void a completed purchase — the transaction already succeeded and you need to reverse it.

Corrected from the source document

The original source document described a single tapSDK.cancelTransaction(amount, cardType, transId, uniqueId, orderId) call. That method name doesn't exist in the working SDK — the real, production-verified call is cancelPurchase, documented below under Void a Completed Purchase, and it takes an appId parameter rather than cardType (see why below).

Abort an In-Flight Transaction

tapSDK.abortTransaction();

Takes no parameters. Call this any time after startTransactionFlow if you need to stop the flow before a result is returned — for example, if your own UI has a cancel button while waiting for the card tap.

Void a Completed Purchase

tapSDK.cancelPurchase(amount, appId, transId, uniqueId, orderId);

Parameter	Type	Notes
amount	String	No decimal point — same format as Start a Transaction.
appId	String	The EMV Application Identifier from the original transaction's result, e.g. "A0000000031010". See appId vs. cardType.
transId	String	The transID from the original transaction's result.
uniqueId	String	Same uniqueId used to start the original transaction.
orderId	String	Same orderId used to start the original transaction.

Example:

tapSDK.cancelPurchase("1000", "A0000000031010", "134436", uniqueId, orderId);

appId vs. cardType

The original source document's sample used a cardType parameter with example values like "VISA", "MASTERCARD", "MYDEBIT". The real SDK call takes appId — the EMV Application Identifier (e.g. "A0000000031010") — which is a different field from the transaction result, not just a rename:

Result field	Example value	Use for cancelPurchase
appId	A0000000031010	Yes — pass this straight through as appId.
cardLabel	VISA	No — this is a display label, not accepted by cancelPurchase.

Both fields come back on the original transaction's result — see Flow Overview for the full result field reference.