Shopify/active_merchant — pull request #1326 by nagash (2014-07-25 03:44:57+00:00)
Title: Add unmatched refund feature to Transact Gateway

Allows you to perform a refund with full card details and no previous transaction/authorization token required. Requires the feature to be enabled on your NAB Transact account.

I've tested this with manually with some live details also.