> For the complete documentation index, see [llms.txt](https://bridge-safety-guide.gitbook.io/bridge-safety-guide-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://bridge-safety-guide.gitbook.io/bridge-safety-guide-docs/4-checks-when-a-cross-chain-swap-memo-is-missing.md).

# 4 Checks When a Cross-Chain Swap Memo Is Missing

A memo tells a receiving system what to do with a transaction or which account to credit. Some chains carry that instruction in a memo field; others put it in a contract call or need no extra identifier at all. If your swap is pending or failed, these four checks help you find out whether a memo is missing, misplaced, or simply not used on that route.

### 1. Identify which kind of memo the transaction needs

A swap memo and a destination tag solve different problems. A swap memo describes an action, such as swapping an asset and naming where the output should go. A destination tag or payment ID helps a shared wallet, often at an exchange, credit a deposit to the right customer.

The chain determines how the instruction travels. Bitcoin transactions can put a memo in an OP\_RETURN output, which is limited to 80 bytes; XRP Ledger transactions have a Memos field; EVM chains such as Ethereum pass the memo through a call to a router contract. A regular transfer to a unique self-custody address may need no separate destination tag.

[thor swap aggregator](https://www.tumblr.com/intrepidserpentastronaut/831089801595863040/what-does-a-cross-chain-route-actually-do) compares routes and shows the selected route’s deposit instructions, helping you check whether the memo belongs in the transaction before you approve it. Read the instruction for the exact source asset and network: the same token name on different chains can use different transaction formats.

### 2. Check whether the destination is shared

A destination tag is needed when the receiving service uses one address for many customers and relies on the tag to sort incoming funds. Sending XRP to an exchange may require its destination tag; sending it to your own wallet usually does not, unless that wallet specifically gives you a tag.

Leaving out a required tag can leave a deposit uncredited even though the transaction succeeded on-chain. Check the receiving service’s deposit page for the exact network, address, and tag, then compare them with the transaction details. Do not add a tag just because the asset sometimes uses one: a tag sent to the wrong place can create a different problem.

### 3. Confirm what the swap route encoded

For a protocol swap, the memo often tells the network the target asset and output address. On a Bitcoin route, it may appear in OP\_RETURN; on an EVM route, the wallet may show a contract interaction whose calldata includes the memo. You might not see a text box labelled “memo” even when the instruction is present.

For example, a Bitcoin-to-ETH swap could put the ETH destination and swap action in the Bitcoin transaction’s memo. If that string is too long for Bitcoin’s 80-byte OP\_RETURN limit, some protocols support a registered reference memo instead. That method has its own setup and expiry rules; it is not safe to omit the memo and assume the amount alone will identify the swap.

In a thor swap flow, use the quote’s deposit instructions rather than copying a memo from another trade. Check that the source network, destination asset, and output address match your intended swap. A typo can make an otherwise confirmed deposit invalid or send the output somewhere unexpected.

### 4. Trace the transaction before taking another action

First, check the source transaction in its block explorer. If it is still unconfirmed, the swap may be waiting for the chain’s required confirmations; that wait varies by network and can stretch when blocks are slow or fees are too low. If it is confirmed, compare the actual destination address and memo or contract call with the instructions shown when you created the swap.

If the transaction is confirmed but the swap remains pending, check the swap interface or route status before sending again. Repeating the deposit can create a second trade. If you sent funds without a required memo, or used the wrong tag, save the transaction hash and contact the service handling the deposit. Recovery may require manual review, and any refund or recovery can take time and incur network fees.

For your next step, write down the source network, transaction hash, confirmation status, and the memo or tag you sent. Compare those details with the route instructions; if they match, wait for processing or ask the service to trace the confirmed deposit. If they do not, contact support with the hash before making another transfer.