Replace-by-fee

Bitcoin fees are an auction for block space. A transaction priced for a quiet moment can wait for hours when demand jumps. Replace-by-fee (RBF) lets the sender broadcast a new version of the same transaction with a higher fee. Because both versions spend the same coins, the network can only ever accept one of them.

A safe replacement keeps the recipient and amount the same and takes the extra fee from the change output. If a transaction has no change, there's nothing to raise the fee from, so it can't be bumped this way.

On Valtu

Every Bitcoin payout is built so it can be replaced. If it's still unconfirmed 30 minutes after broadcast (roughly three blocks), Valtu re-prices it at a higher fee rate and broadcasts the replacement: same coins, same recipient, same amount, with only the change and so the fee different. The transfer keeps one id; its record lists the replaced transaction hashes, and the webhook reports the hash that confirmed. Size payout wallets so payouts leave change, and they can always be bumped.