Why do some non-custodial swaps ask for a refund address on the destination chain

05 September 2026

They ask for a refund address because the swap can fail after your coins leave your wallet but before they arrive on the destination chain. That address is the only way to get your funds back if something goes wrong mid-protocol.

A non-custodial cross-chain swap works in phases. You send coins on the source chain. A counterparty or a smart contract releases coins on the destination chain. Between those two events, the swap is exposed to network congestion, miner reorgs, expired time locks, or a counterparty who stops responding. If the destination leg never executes, your source coins are already gone. Without a return address, they are irretrievable.

How failure happens

Consider a swap from chain A to chain B. You send 1 ETH on chain A. The protocol locks it or escrows it. The other side is supposed to send you, say, 1000 USDC on chain B. But chain B is congested. The transaction sits unconfirmed past the timeout. Or the counterparty's node crashed. Or the price moved so much that the swap's economic incentives broke. In any of those cases, the USDC never arrives.

Your ETH on chain A is already committed. The protocol must reverse the swap. It sends your ETH back to the address you provided on chain A. If you gave no refund address, the coins might be locked forever, or they might go to a burn address, or they might sit in a contract that nobody can access. The refund address is your safety net.

Why not always ask?

Some swaps do not ask for a refund address. Those swaps usually use a different mechanism. For example, a hash time-locked contract (HTLC) on both chains can be set up so that if one leg fails, both sides reclaim their original coins automatically. No refund address is needed because the contract itself enforces the rollback. But HTLC swaps between different blockchains require both chains to support the same cryptographic primitives and timelock logic. Many chains do not.

Simpler, faster swap protocols skip the two-way HTLC. They rely on a single escrow on the source chain and a payout on the destination chain. Those protocols cannot roll back automatically because the destination chain has no corresponding lock. The refund address is the manual override for that gap.

What you need to know about the address

The refund address must be one you control. If you give an exchange deposit address or a smart contract address, recovery becomes someone else's problem. You might get your coins back, but you might not. Some protocols also require the refund address to match the sending address on the source chain. Others allow any address. Check the specific swap interface.

The address is only used if the swap fails. Most swaps succeed. The refund address sits unused. But when it is needed, it is the only way to undo the transaction.

Relation to the broader topic

This entire set of pages is about getting an asset from one chain to another without a bridge or a centralised account. The refund address is a practical detail inside that process. If you want to see how a complete cross-chain swap works from start to finish, the hub page "Swapping crypto across chains" lays out the full flow. The refund address is one of the safety features that makes those swaps work without a custodian holding your money.

Summary

Non-custodial swaps ask for a refund address on the destination chain because the swap can fail after your source coins are sent. The address is the recovery mechanism. Without it, failed swaps mean lost coins. Always provide an address you control. Most swaps complete fine. The refund address is insurance you hope never to use.

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