Refund a Payment

Initiates a refund against a completed payment, identified by its `transactionId` in the path. Omit `refundValue` for a full refund; supply it (amount in minor units) for a partial refund. When provided, the currency must match the original payment. CrissCross executes refunds in one of two ways depending on what the originating provider supports: a **provider refund** through the provider's native refund API, or a **payout refund** that returns the funds via a payout to the original destination. The latter is used when the originating provider does not expose a refund API — common for mobile money, and applicable to bank methods when full account details are held. Both paths are tracked against the original payment so the refundable balance is enforced uniformly. See the [Refunds guide](/full-and-partial-refunds) for details. Eligibility (ownership, refundable state, refund window, and cumulative amount ≤ original) is validated when the refund is initiated. Call [Get Payment Refundability](#operation/getRefundability) beforehand to check whether a payment can be refunded and for how much. Refunds are processed asynchronously. The response is a **refund transaction** in a non-terminal state; track completion by polling [Retrieve Payment Status](#operation/getTransaction) with the returned refund `transactionId`, or by subscribing to the `refund.completed`, `refund.failed`, `refund.errored`, and `refund.cancelled` webhook events.