ChainTax
Built for the 2025/26 UK filing season

Know what needs fixing before you file.

Import exchange CSVs or connect read-only DeFi wallets. ChainTax applies HMRC matching, puts the biggest tax risks first, and shows exactly how every figure was calculated.

Import your trades freeScan a DeFi wallet

200 transactions free · No card required · From £49 per tax year

HMRC share matching
Filing-readiness checks
Line-by-line working
chaintax.co.uk/reportIllustrative

Tax year 2025/26

Tax report

Ready to file

Filing readiness

10 of 10 checks passed

100%

Total gains

£18,420

Taxable gain

£15,420

Estimated CGT

£2,775.60

Every transaction has a tax treatment
Purchase history and cost basis are complete
Prices and Section 104 pools are checked
Income details and tax band are confirmed
PDF · CSV · Audit packShow Working included on every disposal
Show Working

Every disposal,
fully shown.

A report total is hard to verify on its own. ChainTax shows the matching rule applied, the S104 pool before and after the sale, the price source, and a confidence rating for every disposal in your report.

  • HMRC matching rule applied (Same-day, B&B, or Section 104)
  • Pool cost basis before and after the disposal
  • Price source (Kraken, DefiLlama, CoinGecko, or your manual entry)
  • Confidence rating: High, Medium, or Low

Your accountant can verify each line through a revocable, read-only report link. Choose a frozen snapshot or the current report; they never receive access to your dashboard. See the accountant workflow.

chaintax.co.uk/transactions
DisposalHHigh confidence3 Jul 2024
Sold
1.5000 ETH
Gain
+£1,847.50
Matching rule
Average cost (HMRC Section 104)

No same-day or 30-day acquisition matched, so the sale draws from your S104 pool at average cost.

S104 pool
Units
Cost basis
Before
8.2400 ETH
£18,492.00
This disposal
−1.5000 ETH
−£3,366.07
After
6.7400 ETH
£15,125.93
Proceeds £5,213.57·Cost £3,366.07
Price: Kraken close
Audited
Independent route review

Code review completed April 2026, covering auth, payments and concurrency. Read the scope.

4,800+
Automated tests

Tax engine, classifiers, pricing, API routes.

HMRC-native
Section 104 + SA108 Box 51

Same-day, 30-day B&B, S104 pooling. Split-year CGT auto-computed for 2024/25.

One-time
No subscription

Pay per tax year. 14-day refund before download. Secure payment via Stripe.

Gold
InnovateNI Innovator

Gold-level Innovator awarded by InnovateNI, April 2026.

Built by a UK crypto investor. Read our story →
CARF data collection started 1 January 2026

Your records need to tell the same story

In-scope cryptoasset service providers began collecting reportable user and transaction data on 1 January 2026. Their first reports, covering 2026 activity, are due to HMRC by 31 May 2027.

The online deadline for your 2025/26 Self Assessment is 31 January 2027. Build it from complete exchange and wallet records now, with missing purchase history and unresolved transactions made visible.

Read the confirmed CARF timeline

Already received an HMRC letter? Follow the evidence-first response guide →

1 Jan 2026

In-scope providers began collecting reportable user and transaction data

31 Jan 2027

Online filing deadline for the 2025/26 Self Assessment tax year

31 May 2027

First CARF reports covering 2026 activity are due to HMRC

Free estimate

Get a quick read on your wallet

Paste a public wallet address for a rough gain and Capital Gains Tax estimate in about 30 seconds. It is a starting point, not your final report, and we never ask for keys or permissions.

  • Scans your 50 most recent transactions across 5 chains
  • Spots disposals and estimates the gain at HMRC rates
  • No signup, and your first full scan is free when you are ready

Just curious how the sorting works? Paste any transaction hash and see it sorted free →

Free · No sign-up

Not sure where you stand?

Paste a wallet, get an estimated tax bill in 30 seconds. No signup needed.

Or classify a single transaction by pasting any hash, no wallet needed.

Two paths to your HMRC-ready report

How it works

Exchange trades or DeFi activity. Same engine, same accuracy.

Exchange users
01

Export your CSV

Download your transaction history. Native import covers Coinbase, Binance and Kraken; Crypto.com App (beta).

02

Import and sort

Upload your CSV. Supported rows are normalised automatically; anything incomplete or unrecognised stays visible for review.

DeFi users
01

Connect your wallet

Paste your Ethereum, Arbitrum, Optimism, Base, or Polygon address. Read-only, with no seed phrase and no permissions.

02

Automatic sorting

34 protocol-specific detectors cover supported swaps, LPs, staking, liquid restaking (ether.fi, Renzo, Kelp), bridging, and more. Anything unresolved enters Needs Review.

Both paths, from here
03

HMRC matching applied automatically

Same-day rule, 30-day Bed & Breakfast rule and Section 104 pooling, all applied in the correct order. Every disposal shows its working.

04

Download your report

PDF tax report with SA108 box values pre-filled. Hand it to your accountant or file it yourself.

Try a free import →
Live holdings

Your holdings,
valued for tax.

A report is a snapshot of the year. ChainTax also keeps a live view of what you still hold: current market value, your Section 104 cost basis, and the unrealised gain or loss on every position, all from the same engine that builds your report.

  • Live market value and cost basis for every token you still hold
  • Unrealised gain or loss, using the same S104 pool as your report
  • Tokens and NFTs together, with no floor-price guessing on NFTs
  • History builds forward from the day you start, with no invented back-history
  • Export to CSV, or share a read-only snapshot

Not tax advice. A live read on where you stand. See how the holdings view works.

chaintax.co.uk/holdings
Portfolio value
£20,986.00
Unrealised
+£1,966.07
Asset
Market value
Unrealised
ETH 6.7400
£17,524.00
+£2,398.07
USDC 3,000.00
£2,982.00
£0.00
ARB 1,200.00
£480.00
−£432.00
Cost basis from your Section 104 pools
History builds from today

See what is automatic, and what still needs review.

ChainTax makes its coverage boundary visible. Supported exchange and DeFi activity is classified automatically; gaps and uncertain cases stay in a Needs Review queue. You can calculate your crypto tax and inspect the working on your own figures.

Exchange buy / sell

Automatic

Normalises supported CSV rows into the same HMRC calculation

Review boundary

Missing prices, history gaps and unsupported row types stay visible

LP position (add / remove)

Automatic

Supported protocol handlers record both sides and apply the configured tax stance

Review boundary

New or unsupported pools enter Needs Review

Staking rewards

Automatic

Supported reward claims are recorded at fair market value

Review boundary

Accruals without an observable claim may need manual evidence

Bridge transfer

Automatic

Supported bridge contracts are classified from the on-chain flow

Review boundary

Ambiguous or different-token legs are flagged instead of assumed

HMRC matching rules

Automatic

Same-day, 30-day and Section 104 run automatically in priority order

Review boundary

Missing acquisition history remains a named filing check

Show Working

Automatic

Each disposal shows its rule, pool movement, cost, proceeds and price source

Review boundary

Low-confidence prices and manual overrides remain identifiable

Exchanges + DeFi combined

Automatic

Connected sources feed one cross-platform Section 104 pool

Review boundary

Only the sources you import or connect can contribute history

Split-year CGT (2024/25)

Automatic

Disposals are split around 30 October and Box 51 is calculated

Review boundary

Salary and filing inputs still need user confirmation

Holdings

Automatic

Shows tax-oriented cost basis and unrealised gain/loss

Review boundary

Snapshot history starts when the feature begins recording it

Manual entry, shared report links, NFT trades, airdrops and more: see the full comparison →

Koinly vs ChainTax →CoinTracker vs ChainTax →Recap vs ChainTax →

One price. One tax year. No surprises.

Pay once, download your report. No subscriptions, no per-transaction fees.

Free

£0forever

200 transactions

See your full report. Pay only to unlock final amounts

Light

£49/tax year

2,500 transactions

Exchange trades, staking, a few swaps

Most popular

Active

£99/tax year

10,000 transactions

Active across exchanges and DeFi

Preview the calculation before paying. Above 10,000 transactions? Concierge sync is quote-first, run by us.

Compare tiers in detail
What ChainTax doesn't do yet

No tax tool is perfect. Here's what ChainTax cannot yet handle automatically, and what you should check manually or discuss with your accountant.

  • •Lido stETH rebase rewards happen at the protocol level and rarely appear as transactions in your wallet, so ChainTax now detects them automatically from your stETH balance growth and books each as income at its market value on the date received. It covers every stETH wallet on your account: add another and your next sync recalculates your rebase rewards across the complete set.
  • •Deposits into Aave, Compound, Yearn, EigenLayer, and similar fixed-ratio lending or staking protocols are treated as transfers, not disposals, so your cost basis carries to the receipt token (aToken, cToken, vault share). HMRC's strict reading (Cryptoassets Manual CRYPTO61620) could treat these as deemed disposals at deposit; HMRC confirmed in November 2025 that it is developing no-gain-no-loss rules matching the treatment ChainTax applies today, but they are not yet law. If you want strict-reading compliance, override the deposit event manually.
  • •Some protocols return ETH via internal calls (Nexus Mutual, Rocket Pool, cbETH). We catch most of these automatically; when we can't, we flag the event for your review.
  • •Five EVM chains supported: Ethereum, Arbitrum, Optimism, Base, and Polygon. Other chains (Solana, Avalanche, etc.) are not yet covered.

Full detail: How it works → Known limitations

Common questions

The things people ask before they sign up.

Is it safe to connect my wallet?
Yes. ChainTax only ever sees your public wallet address, which is read-only on-chain data. We never ask for a seed phrase, private key, or any signing permission. The same data anyone with your address can see on Etherscan is what we use to build your report.
How accurate is the automatic classification?
Every disposal is matched against HMRC rules in the correct order: Same-day → 30-day Bed & Breakfast → Section 104 pooling. 34 protocol-specific detectors cover supported activity across Uniswap, Aave, Lido, Curve, GMX, liquid restaking (ether.fi, Renzo, Kelp), and more. Anything we cannot recognise lands in a Needs Review queue rather than being presented as resolved.
What if a transaction is misclassified?
Edit it. Every transaction has an Edit button. Change the type, set the proceeds, set the cost basis, override the asset. Your edit is preserved on every future re-sync, so you only need to fix something once. The report regenerates automatically.
Can my accountant verify the calculations?
Yes. Generate a shareable read-only link from your report. Your accountant sees every disposal, every matching rule, the cost basis before and after each sale, and the price source. No login needed on their side. The PDF report also pre-fills SA108 box values (13.1–13.8 plus Box 51 split-year adjustment for 2024/25).
Which exchanges and chains do you support?
CSV import: Coinbase, Binance and Kraken; Crypto.com App (beta); plus Koinly CSV. 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.
On-chain: Ethereum, Arbitrum, Optimism, Base, and Polygon. Solana, Avalanche, BSC and others are not yet covered. For those, manual entry or a Koinly CSV is the workaround for now.
What about NFTs, staking rewards, or trades I made before signing up?
NFT marketplace trades on OpenSea, Blur, and Treasure Trove are auto-classified with FIFO cost basis tracking. For NFTs from other marketplaces, add the cost basis manually, once. Staking rewards on supported protocols (Lido, Rocket Pool, Curve, Atlas Mine, Synthetix) are picked up automatically. For pre-sync activity that we cannot reconstruct from on-chain history, the manual-entry flow lets you add buys, sells, and income at the right historical price.
Why is ChainTax cheaper than other crypto tax tools?
ChainTax is priced around a single UK filing year rather than year-round portfolio access. You pay £49 for Light (up to 2,500 transactions) or £99 for Active (up to 10,000 transactions). There is no subscription or automatic renewal. Other providers use different plan scopes, so compare report years, integrations and transaction limits as well as headline price.
I had over 10,000 transactions last year. Now what?
Concierge sync. We run the import on a service account, walk through any Needs-review items with you, and hand you the same report you would have gotten self-serve. Quote-first, typically £249–£449 depending on portfolio shape. Email hello@chaintax.co.uk with your wallet address and we will reply with a quote.

Still have questions? hello@chaintax.co.uk. We read every email.

Popular guides

Why your Coinbase tax report isn't enough for HMRCSection 104 pooling: the UK crypto cost-basis ruleFiling crypto on your 2025/26 Self AssessmentPayments on account: why July ignores your crypto gains

Start free. Pay only when the report is ready.

Bring exchange trades and DeFi wallets into one HMRC-ready record. Fix the items that matter, check every calculation, then unlock the final PDF and CSV when you are satisfied.

Build your tax report free

200 transactions free · 14-day refund before download · Stripe secure