What is the backup card for?

The backup card covers what a payout can't: a carrier shipping correction and the correction fee on it, a refund on an order whose payout already reached you, or a chargeback when a buyer's bank reverses a payment you were already paid for. It is only ever charged against a real order, and you are notified every time it happens.

It is required before you can buy a shipping label, and payouts do not release without one on file. Add it under Account, then Payouts.

If the card is missing or declines, the amount is deducted from your next payout instead. The debt never grows quietly and is never written off silently.