How do I match a swap across two different blockchains for my own records

07 September 2026

You match a swap across two blockchains by linking the transaction hash from the source chain to the transaction hash from the destination chain through the exchange record provided by the swap service. The exchange record is the single document that ties together the input transaction on one chain and the output transaction on another.

Why matching is not straightforward

A cross-chain swap is not a single blockchain event. It is two separate on-chain transactions, often occurring minutes apart, on different networks that have no direct communication. The source chain records the outgoing tokens. The destination chain records the incoming tokens. Without a linking record, these two transactions appear unrelated to any observer.

The swap service you used acts as the intermediary. Its internal system generates a swap ID or order ID. That ID is the key that matches the two transactions. Your exchange record - email confirmation, order page, or API response - contains that ID alongside both transaction hashes. Save that document. It is the only proof that the two on-chain events belong to the same swap.

What to collect from each chain

For the source chain, record: - The transaction hash of the outgoing transfer. - The block number and timestamp. - The wallet address you sent from. - The token and amount sent.

For the destination chain, record: - The transaction hash of the incoming transfer. - The block number and timestamp. - The wallet address that received the tokens. - The token and amount received.

The exchange record should contain all eight pieces of data. If it does not, you can reconstruct the link by searching for the source transaction hash on a block explorer and then looking for a corresponding destination transaction in the same wallet address within a plausible time window - but this is imprecise and may fail if the swap service uses intermediary wallets.

How to verify the match yourself

1. Open the source chain block explorer. Paste the source transaction hash. Confirm the amount and destination address (often a swap service contract or hot wallet).
2. Open the destination chain block explorer. Paste the destination transaction hash. Confirm the amount and the source address (again, often a service wallet).
3. Compare the timestamps. They should be close, usually within seconds to a few minutes.
4. Cross-check the swap ID from your exchange record. Some services embed the swap ID in the transaction data of one or both chains. Look for it in the "input data" field of the source transaction.

When the exchange record is missing

If you lost the exchange record, matching becomes difficult. You can try to find the destination transaction by searching your destination wallet address on the destination chain block explorer, filtering by time and token type. But without the swap ID, you cannot prove the two transactions are causally connected, only that they occurred near each other. For tax purposes, that may not satisfy an auditor.

How this fits your tax trail

The hub page "Proof you swapped for your tax trail" explains why this matching evidence matters for your records. That page covers the broader principle: a swap is not a single event, and your tax report must show the complete chain of custody from one asset to another. The matching method described here is the technical step that makes that chain provable.

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