What does a failed swap look like on Polygonscan and what should I save from it

07 September 2026

A failed swap on Polygonscan shows as a transaction with a status of "Failed" in red text, and you should save the transaction hash, the error reason (if visible), and the block number. The failure is not ambiguous - the blockchain either executes the swap or it does not, and the record of that outcome is permanent.

How to identify a failed swap

On Polygonscan, every transaction appears with a status indicator. A successful swap shows a green checkmark and the word "Success." A failed swap shows a red circle with the word "Failed." The distinction is immediate on the transaction overview page. Below that, the "From" and "To" addresses show the wallet and the contract that handled the swap, exactly as they would for a success.

The critical difference is in the "Transaction Action" section. For a failed swap, this section may be blank or display only partial data. The tokens never moved. The logs that would normally prove the transfer of token A for token B simply do not exist. If you click into the "Internal Txns" tab, it will often show zero internal transactions. The swap contract attempted the trade, hit a condition it could not meet, and reverted everything except the gas fee.

What to save from a failed swap

Save the transaction hash. That hash is the single piece of evidence that proves the swap was attempted and failed. Without it, you have only a memory and a missing balance. On Polygonscan, copy the hash from the URL bar after the transaction page loads, or from the "Transaction Hash" field at the top of the page.

Save the error reason. Polygonscan displays a "Revert reason" line on the transaction details page when the contract emits one. Common reasons include "insufficient output amount," "transfer failed," or "execution reverted." Not all failed swaps show a revert reason - some return only a generic failure. If a reason is present, copy the full text. It tells you why the swap did not go through: the price moved, the liquidity pool ran dry, or the slippage tolerance was too tight.

Save the block number. The block number places the failure in time. Without it, you know only that the swap failed at some point. With the block number, you can check the state of the liquidity pool, the price at that moment, and confirm that no tokens left your wallet. All of that is discoverable from the block number alone.

Save the gas fee. The transaction used gas even though it failed. Polygonscan shows the gas used, the gas price, and the total fee in MATIC. That fee is a real cost. If you are tracking expenses for tax or reconciliation purposes, that fee is a deductible loss - it is money spent on an attempt that yielded nothing. Screenshot the "Transaction Fee" line.

Why it matters for tax records

The hub page under which this answer sits is "Which swap records to keep for tax time." A failed swap is not a trade. You did not acquire a new token, and you did not dispose of the token you intended to swap. The failure means your cost basis in the original token remains unchanged. But the fee is a transaction cost. Many tax regimes allow you to deduct transaction fees against capital gains, and a failed swap fee is no different from a successful one in that regard. The problem is proving it. Without the saved hash and fee record, you have no evidence that the fee was paid or that the swap failed. An auditor sees only a missing balance and a fee outflow. The saved Polygonscan page connects the two.

What a failed swap does not prove

A failed swap does not prove you owned the tokens you tried to swap. It proves only that your wallet attempted the transaction. To prove ownership, you need the transaction that funded the wallet with those tokens, or the swap that brought them in. A failure alone is not a receipt of ownership. It is a receipt of an attempt. That distinction matters if you ever need to explain why a balance in your wallet does not match your records.

Save the full Polygonscan page as a PDF, or take a screenshot that captures the status, the hash, the block number, and the fee. Text copies of the hash and block number are fine, but a visual record includes the timestamp and the network confirmation that the data is live. A text file can be fabricated. A screenshot of the Polygonscan UI carries more weight.

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