Auto Sync with Arbitrum Bridge ETH onto Arbitrum, swap across a couple of its decentralised exchanges, and pick up an airdrop along the way. What started as one transaction is now scattered across a dozen. None of it shows up as a single balance you can hand to an accountant.
Add your Arbitrum address to Recap and it reads that activity straight from the chain. That covers swaps, bridge deposits, gas paid in ETH and any rewards. Recap classifies each entry and works out the gain, loss or income under your tax residency's rules. The report below comes from your own on-chain history, not a guess.
Disclaimer
The information provided in this content does not endorse Arbitrum. Furthermore, it does not constitute tax advice. If anything financial or tax-related is unclear, speak to a qualified tax professional. You can also share your Recap account with your accountant or tax adviser directly.
Why on-chain history on Arbitrum is difficult to reconcile
An Arbitrum address gives you a full record of what happened, but it is a list of contract calls, not a statement. A few things make the tax side harder than it looks:
Bridging is not the same as buying
Moving ETH or a token from Ethereum onto Arbitrum through the canonical bridge is not a disposal. It is the same asset arriving on a different chain. It is easy to mistake for a sale, and it can sit pending for a few minutes while it finalises.
Swaps and DeFi positions add up fast
Arbitrum carries a large share of Ethereum's decentralised exchange and lending activity. A couple of afternoons of trading across different apps can generate more disposals than a year of exchange trading. Each swap is a disposal even though no ordinary money changes hands.
Gas is paid in ETH, not in whatever you are trading
Every transaction costs a small amount of ETH in gas, even when the trade itself is between two other tokens. That gas payment is a disposal of the ETH spent, on top of whatever the transaction itself does. It is one of the easiest costs to leave out of a manual reconciliation.
How to add your Arbitrum address to Recap
Arbitrum imports into Recap from your public address, the same one you already use on the network. Add it once, and Recap reads your full on-chain history automatically, including receives, sends, swaps, bridge deposits and fees. It stays up to date as new transactions land.
How Arbitrum activity is taxed
Tax treatment depends on the transaction type and where you are tax resident. Here is how the main Arbitrum activities are generally treated:
Swaps and DEX trades
Swapping one token for another, including trades into stablecoins, is a disposal of the token you give up. It is also an acquisition of the token you receive, each measured against your cost-basis pool.
Bridging between Ethereum and Arbitrum
Bridging through the canonical Arbitrum bridge is not a disposal, since it is the same asset arriving on Arbitrum rather than a sale. The same applies moving funds back the other way, and to transfers between your own accounts on either chain.
Network fees
Paying a gas fee in ETH is a disposal of the ETH spent. The fee also becomes part of the cost basis of the transaction it relates to. It affects your gain or loss twice over rather than once.
Rewards and airdrops
Reward tokens earned through a protocol on Arbitrum are treated as income at their value when they arrive. That value also becomes their cost basis going forward. An airdrop, such as the ARB distribution in March 2023, works differently. It is recorded as an acquisition rather than income, since you did nothing in exchange for it.
| Transaction type | CGT disposal | CGT acquisition | Income |
|---|---|---|---|
| Swapping one token for another | CGT disposal: yes | CGT acquisition: yes | Income: no |
| Bridging between Ethereum and Arbitrum | CGT disposal: no | CGT acquisition: no | Income: no |
| Transferring between your own accounts | CGT disposal: no | CGT acquisition: no | Income: no |
| Network and gas fees | CGT disposal: yes. Paying a fee in ETH disposes of it, and the fee also becomes part of the cost basis of the transaction it relates to. | CGT acquisition: no | Income: no |
| Reward tokens received on-chain | CGT disposal: no | CGT acquisition: yes. The reward also enters the section 104 pool at the same market value used for the income figure. | Income: yes |
| Airdrops, including ARB | CGT disposal: no | CGT acquisition: yes. Recorded as an acquisition rather than income. Recap's default for portfolios created after 6 April 2024: the airdropped asset enters the pool at zero cost. Portfolios created before then default to market value. Configurable per portfolio and overridable per transaction. | Income: no |
This table shows how Recap classifies each transaction type by default. Some treatments — such as the acquisition cost used for airdrops — are configurable in Recap. This is general information, not tax advice; consult a qualified tax professional about your circumstances.
This table shows Recap's default classification for common Arbitrum activity. It is not an exhaustive list or a ruling on your own position, and the right treatment can depend on your circumstances and jurisdiction. Confirm anything material with a qualified tax adviser, and recategorise any transaction where your facts differ.
Refer to our UK crypto tax guide and US crypto tax guide for a fuller look at how these rules apply.
What we handle on Arbitrum that Arbiscan does not
Arbiscan shows you every transaction, but it does not say which ones are disposals. It does not value anything at the point you received it, or carry a cost basis forward between transactions. Recap does all three, and keeps your cost-basis pool consistent across everything you do on the chain.
We have also kept improving how Arbitrum syncing works. An error fetching transactions was fixed in December 2024, and a sync failure affecting some transaction types was fixed in August 2026. If your history has ever looked incomplete, it is worth re-syncing your account.
What's in your Arbitrum tax report
Recap turns your Arbitrum activity into a single tax report. Swaps are treated as the disposals and acquisitions they are, and bridge deposits and transfers between your own accounts are excluded. Gas fees are counted as disposals and folded into the cost basis of the transactions they relate to.
Capital gains, losses and income are worked out under the rules for your jurisdiction. The result is a clear year-by-year summary you can file yourself or hand to your accountant.
Why Arbitrum users choose Recap
Arbitrum users choose Recap because a raw address, full of bridge deposits, swaps and gas payments, is slow and easy to get wrong by hand. Bring it into Recap instead, and your gains, losses and income come back as one report, ready to file or hand to your accountant.
