Simulate a merchant cancelling a card authorization before it settles — a hotel releasing a hold, or a store voiding a purchase that never went through. Use it to see how your integration handles an authorization that disappears without ever clearing. Send amount to reverse only part of the authorization, or leave it out to reverse all of it. The transaction must still be fully open: once any part of it has settled, it can no longer be reversed. Grid processes the reversal in the background. A full reversal sets status: VOIDED and sends a CARD_TRANSACTION.VOIDED webhook. A partial reversal leaves the transaction AUTHORIZED with a smaller hold.

Production returns 404 on this path.

{
  "cardTransactionId": "Transaction:019542f5-b3e7-1d02-0000-000000000100",
  "amount": 1250
}

{
  "issuerTransactionToken": "f3a1c2d4-5b6e-7890-abcd-ef0123456789"
}