How to Do Your MetaMask Crypto Taxes: One Address, 14 Networks

Overview

MetaMask makes multi-chain activity almost invisible. You switch networks from a dropdown, the address at the top of the window never changes, and the balance updates. It feels like one account moving between views of itself.

For tax reporting it is the opposite. That single 0x string is a separate, independent account on every network it touches, each with its own transaction history, its own fee coin, and its own explorer. Ethereum does not know what your address did on Arbitrum. Arbitrum does not know what it did on Polygon.

Import one network and you get one network's history. This article covers how to get all of them, and which parts of a MetaMask history are most often lost.

The Same Address, Fourteen Times

Every EVM network derives addresses the same way, which is why yours works everywhere without any setup. It is also why nothing about your address tells you which networks you have used — you have to know.

CryptoTaxBridge supports these networks for an 0x address:

Network	Fee paid in
Ethereum	ETH
Polygon	POL
Arbitrum One	ETH
Linea	ETH
Gnosis	xDAI
Avalanche	AVAX
Blast	ETH
Mantle	MNT
Sonic	S
Unichain	ETH
opBNB	BNB
Berachain	BERA
Taiko	ETH
World Chain	ETH

Add the address once per network you have used. An import for a network you never touched simply returns nothing, so when in doubt, import it — an empty result costs you a minute, while a skipped network costs you the acquisition history of whatever you later sold.

MetaMask now also supports Bitcoin and Solana. Those use entirely different address formats and are imported separately, and Bitcoin in particular needs an extended public key rather than an address.

Import a MetaMask wallet

Accounts You Forgot You Made

MetaMask lets you create additional accounts inside the same wallet with one click, and each one is a genuinely different address.

People make a second account to keep a risky protocol away from their main holdings, or a third for a mint, and then stop thinking about it. Two years later the original account is the one they remember, and the forgotten account is where an old purchase sits.

Open the account list before you import and go through it properly. A hardware wallet connected through MetaMask adds its own accounts on top, and imported accounts from other seed phrases add more.

Bridging Is Not Automatically a Transfer

Moving an asset from Ethereum to an L2 feels like moving money between your own pockets. HMRC's position is more careful than that, and worth quoting accurately: the answer depends on the facts.

The guidance distinguishes two situations. Where the transfer is irreversible and you end up holding the same token on a different ledger, HMRC applies section 43 of the Taxation of Chargeable Gains Act — the original allowable cost carries across to the tokens you now hold, and the gain or loss is calculated when you eventually dispose of them. Where a smart contract gives you a different token in exchange, the manual offers no blanket treatment and says the outcome depends on the circumstances.

That second case covers a lot of real bridging. Wrapped assets, liquidity-network bridges that hand you a synthetic representation, and anything where the token you receive is not the token you sent all sit there.

The practical takeaway is not a rule but a requirement: your report needs both sides of every bridge, on both networks, with dates and amounts. Without that, neither treatment can be applied. With it, you or your adviser can take a position and evidence it.

Approvals, Failed Transactions and Gas

A MetaMask history contains a lot of transactions where no token moved.

Every interaction with a decentralised exchange begins with an approval. Every busy day produces at least one transaction that reverted. Every consolidation and every self-transfer costs gas without disposing of the asset being moved.

These matter because the fee is real even when the transaction achieved nothing. HMRC lists transaction fees paid for having a transaction included on the distributed ledger among allowable costs, and paying gas is itself a disposal of the coin used to pay it.

Simple importers drop these rows because there is no token transfer to anchor them to. CryptoTaxBridge imports them deliberately, so expect to see transactions in your history that appear to do nothing. What is deductible and what is not covers where the line sits.

Airdrops and Unsolicited Tokens

Anyone can send any token to any address. A MetaMask address that has been active for a few years will have accumulated tokens nobody asked for: promotional airdrops, dust, phishing lures designed to get you to visit a contract, and outright fakes impersonating real projects.

These appear in your imported history because they genuinely happened on-chain. Deciding what they are is a judgement call, and it is yours rather than the software's — a claimed airdrop from a protocol you used may well be taxable income, while a token that appeared unbidden from an unknown contract is generally not something you have received in any meaningful sense.

CryptoTaxBridge does not try to guess. Automated spam detection discards real transactions often enough to be dangerous, so every transaction can be reviewed and deleted instead, and restored later if you change your mind. On a first import of an old address, budget time for this pass.

Review imported transactions

DeFi Positions Need Both Ends

Adding liquidity, taking it out, wrapping, staking through a contract — each of these is multiple asset movements bundled into one transaction.

An import that decomposes them into unrelated deposits and withdrawals produces a history that is technically accurate and useless: two assets left, one arrived, and nothing connects them. The gain calculation then has nothing to work with.

When reviewing a DeFi-heavy history, check that transactions involving several assets arrived as coherent events rather than scattered fragments, and that anything you received as a reward is recorded as income at the point you received it, not as a mystery deposit.

A MetaMask Import Checklist

Before generating a report, confirm:

every network you have used is imported, including L2s you tried once;
every account in the wallet is covered, not just the first;
any hardware wallet connected through MetaMask is included;
both sides of every bridge appear, on both networks;
outgoing transactions carry a gas fee;
exchanges you funded the wallet from are connected;
unsolicited tokens have been reviewed.

Conclusion

MetaMask's convenience is that it hides the boundaries between networks. Its tax cost is that those boundaries are exactly what a report has to respect.

Treat each network as its own source, import the ones you used, and check that the awkward transactions — approvals, failures, bridges, self-transfers — survived the import rather than being tidied away. What remains is a history that supports a number rather than a history that produces one.

Generate a tax report

Official Resources

This article provides general information and is not tax advice. The treatment of bridging depends on the facts of each transaction; take professional advice where amounts are material.