Refunds a card charge in full or in part. Call it more than once to refund in steps, up to the amount still refundable. Only charges in paid or partially_refunded state can be refunded. Sandbox credentials only see sandbox charges and live credentials only see live charges.

Send an Idempotency-Key header. Without one, the key is derived from the transaction and amount, so an identical retry is collapsed, but two deliberate partial refunds of the same amount would also be collapsed.

Your balance is debited when the refund is processed, not when this call returns. You also receive refunded or partially_refunded callbacks and CARD_REFUND callbacks when the refund changes state.

This endpoint stays available for accounts limited to refunds (REFUND_ONLY).