How ChainTax works
From scattered crypto history to tax working you can review.
ChainTax does more than produce a total. It brings supported sources together, applies the UK rules, shows the calculation, and keeps anything that could change the answer visible.
The product journey
The calculation is automatic. Trust still has to be earned.
The four stages stay separate so a completed import cannot be mistaken for a report whose important evidence has been checked.
- 1
Bring the history together
Import supported exchange files and add public wallet addresses. ChainTax combines them account-wide without private keys or signing permissions.
- 2
Build the calculation
Supported activity is classified and priced in pounds, then acquisitions and disposals are matched in the UK statutory order.
- 3
Resolve what could change it
Missing history, uncertain material activity, unavailable taxable prices, and stale calculations remain named checks instead of being hidden.
- 4
Inspect and share the working
Open each material disposal, download PDF and CSV reports, or give your accountant a secure read-only view of the same calculation.
Every sale,
explained.
A total on its own is hard to trust. Open any sale to see how much came in, what the crypto originally cost, which price was used, and how ChainTax reached the gain or loss.
- How the original purchase was matched to the sale
- The purchase cost used in the calculation
- Where the pound value came from
- Anything ChainTax is unsure about
What happens when something is missing?
- 1Flag it. If the original purchase cannot be found, ChainTax marks the figure as incomplete instead of assuming it is correct.
- 2Add the missing detail. Import the exchange file, add the original purchase, or enter a reliable market value.
- 3Recalculate. ChainTax reruns the report and clears the warning only when the issue is fixed.
Open every calculation yourself or send your accountant a secure, read-only link. They can see the report, but never your dashboard. See how sharing works.
There were no matching purchases on the same day or in the following 30 days, so HMRC's average-cost rule applies.
Review checks
The report tells you what could still change the answer.
ChainTax can calculate the supported parts of a history while still withholding a positive accountant-review state. That is deliberate: a number is not presented as settled while material evidence is missing.
Read the exact review gatesSource history
Are the relevant exchange and wallet periods present?
Classification
Could any unresolved or low-confidence material activity change the tax?
Price evidence
Does every positive taxable event have a supported pound value?
Calculation state
Has the report been rematched after every pool-changing correction?
Current coverage
Built for UK exchange and EVM history, including supported DeFi.
Coverage is specific, not universal. Supported inputs produce repeatable classifications; unfamiliar or incomplete activity remains visible for review.
Before you create an account
Check one source or activity
Search one exchange, chain, protocol or activity at a time. Then check whether you can supply the complete history needed for an account-wide UK calculation.
This check stays in your browser. Do not enter a wallet address, upload a file, or include personal information.
Exchange files
Coinbase, Binance and Kraken; Crypto.com App (beta); plus Koinly universal CSV (compatible format).
The Crypto.com App importer is in beta. It is parser-tested but has not yet been validated end to end against a current real export, so review the imported rows before relying on them.
Read-only wallets
Ethereum, Arbitrum, Optimism, Base and Polygon. Public addresses only; no private keys or signing permissions.
Supported activity
Swaps, bridges, lending, liquidity, staking, NFTs, transfers, and named protocols including ether.fi, Renzo, Kelp, Aave, Lido, and Uniswap.
Corrections and missing history
Your corrections remain part of the record.
Add a missing exchange purchase, correct a classification, enter supported price evidence, or record off-chain activity manually. Pool-changing edits trigger a full rematch so later gains do not keep stale costs.
What the report retains
- The original imported or on-chain source
- The correction, note, or manual record you supplied
- The calculation before and after a pool-changing rematch
- Any remaining uncertainty that still needs review
Holdings
A live view of the tax pools built from your history.
Holdings values the balances reconstructed from your imported history against the same Section 104 cost basis used by your report. It shows the unrealised gain or loss for fungible tokens; an NFT is retained at recorded cost rather than given an invented floor price.
Reconciled view
Token quantity, current value, pooled cost, and unrealised gain are shown together.
Honest history
Daily snapshots build from the day you start, with no invented back-history.
Portable evidence
Export the current holdings view to CSV or share a frozen read-only snapshot.
Simulate
Model a what-if disposal without changing your records.
From Holdings, choose an amount and model a disposal at the latest available GBP price. The calculation uses your real Section 104 pools and applies same-day, 30-day bed & breakfast, then Section 104 matching. Nothing is saved or filed.
Where the data comes from
Units come from your reconstructed holdings. Prices use the same source waterfall as the report: cache, Kraken, DefiLlama, then CoinGecko.
Calculation, not a recommendation
This is not tax or financial advice. ChainTax does not recommend a disposal or its timing. Real results depend on the actual date, price, fees, and any later acquisition within the 30-day window.
Important boundaries
Specific coverage, visible limitations.
These are calculation boundaries, current-law choices, and coverage gaps to review before relying on a report.
- stETH rebases: ChainTax estimates rebase income from periodic wallet-balance snapshots (monthly and at tax-year boundaries), net of transfers, then values the increase on the snapshot date. This covers every fully synced Ethereum wallet on the account, but it is not a daily receipt-by-receipt reconstruction.
- Receipt-token deposits: For supported Aave, Compound V2, Yearn, and Convex actions, ChainTax currently treats decoded deposits and withdrawals as transfers and carries Section 104 basis when both economic legs are present. Missing required legs are sent to Needs review. EigenLayer automation covers StrategyManager LST restaking, not native-ETH EigenPod restaking. HMRC's current CRYPTO61620 treatment depends on beneficial ownership and can treat a token exchange as a disposal. Draft NGNL rules were published on 13 July 2026 for qualifying arrangements from 6 April 2027, but are not yet law. Ask a tax adviser before changing current-period treatment.
- Internal ETH returns: Known Rocket Pool and cbETH methods use trace data to recover ETH returned through internal calls; if that data is unavailable, the event stays in Needs review. Nexus Mutual sales can instead use the NXM market value as a fallback, and the event note says when that happened.
- Chain coverage: Automatic on-chain sync supports Ethereum, Arbitrum, Optimism, Base, and Polygon. Other networks, including Solana and Avalanche, need a supported CSV import or manual records.
Technical reference
Need the exact rules, sources, and coverage table?
The methodology documents classifier coverage, exchange parsing, UK matching, CGT rates, price sources, income treatment, SA108 mapping, holdings, simulation, and current limitations.
Read the methodologyBuild a UK crypto tax report you can review.
Add exchange files or read-only wallets. ChainTax brings the history together, applies UK matching rules, and keeps anything that could change your tax visible.
200 transaction records free account-wide · No card required · One payment per report tax year