What is a merchant transaction ID?¶

A merchant transaction ID identifies an event inside the merchant's sales or payment system. Other providers may not recognise it without a mapping.

It can identify attempt rather than success¶

The merchant may create it at checkout start, payment attempt or completion. Several attempts can share an order, and declines, refunds, reversals or chargebacks can have linked records.

Preserve the merchant context¶

Retain exact ID, source, order, account, amount, currency, time, status and processor reference. Ask which records it links and map it to acquiring and issuer IDs.

The identifier proves a merchant-system event, not payment completion or purchaser identity. Report its creator and defined event explicitly.