ChainTax
Built for UK crypto tax professionals

DeFi clients don't have to be your worst margin.

1,000+ on-chain transactions per client. S104 pools built by hand. Same-day and B&B rules applied manually. ChainTax does all of it — you review the audit trail and sign off.

Built by a UK crypto investor who needed this for his own accountant. Read the story →

Are you a crypto investor wondering if you need an accountant? See our pricing.

Request a demo accountSee how it works

The DeFi client problem

Replace 3 hours of tracing with a 20-minute review

Your client connects their wallets and imports exchange CSVs. ChainTax sorts every transaction across 33 protocols and 5 chains, then shares a read-only report link with you. You verify and file. With CARF cross-matching live from May 2027, the reconciliation step is no longer optional — it's the new default.

Without ChainTax

  • Trace each swap, stake, and LP on Etherscan
  • Build S104 pools in spreadsheets
  • Apply same-day and 30-day B&B rules by hand
  • Cross-reference token prices at disposal time
  • Fill SA108 boxes 13.1–13.8 manually

Result: you eat the margin or turn the client away.

With ChainTax

  • Client connects wallets — sorted automatically
  • S104 pools built per asset from first acquisition
  • Same-day and B&B matching on every disposal
  • Full audit trail per disposal — Show Working
  • Live share link — you always see the current version, no CSV ping-pong

Review in minutes. Bill for advice, not data entry.

1Client signs up2Connects wallets or imports CSVs3ChainTax sorts4Client shares report link5You review and sign off

The feature accountants actually need

Show Working — every line, fully auditable

Every disposal shows the matching rule applied, the S104 pool snapshot before and after, the gain calculation, and the SA108 box it maps to. No black boxes. No "trust us".

  • Same-day, B&B, or S104 matching rule tagged per disposal
  • Pool size and average cost shown before and after
  • SA108 boxes 13.1–13.8 + Box 51 split-year auto-computed
  • Low-confidence results flagged for your review
  • Shared via read-only link — auto-updates after every client edit
DisposalUniswap V3 Swap
High confidence
Disposed
2.4500 ETH
Acquired
7,841.23 USDC
Date
14 Mar 2025, 09:42 GMT
Matching Rule — Section 104 Pool
Pool before
14.8200 ETH @ £1,247.33 avg
Disposed from pool
2.4500 ETH
Allowable cost
£3,055.96
Pool after
12.3700 ETH @ £1,247.33 avg
Gain Calculation
Proceeds
£6,273.18
Allowable cost (S104)
£3,055.96
Gas fee
£4.12
Chargeable gain
£3,213.10
SA108/Box 13.2 (proceeds)/Box 13.4 (gains)

The maths

Time saved per DeFi client

Each client runs ChainTax on their own wallets and exchanges. You review the Show Working output and sign off the return — typically 20–30 minutes instead of 3+ hours of manual reconciliation. One Active tax-year purchase (£99, up to 10,000 transactions) covers a single client's full HMRC return — no subscriptions, no per-seat billing. For higher-volume clients, the Concierge sync is quoted on a per-portfolio basis.

10
1100
3
1 hr8 hrs
£200
£50£500
Manual cost per client£600
ChainTax Active£99
Saving per client+£501
Annual saving (10 clients)+£5,010

in time costs recovered — before accounting for new clients you can now accept profitably.

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.

  • •Aave interest (aTokens) accrues via balance changes rather than individual transactions, so it doesn't appear in your transaction history. For now, add aToken interest manually as an income event — automatic detection via daily balance snapshots is on the roadmap.
  • •Lido stETH rebase rewards happen at the protocol level and rarely appear as transactions in your wallet. Add them manually as income for now — automatic detection via daily balance snapshots is on the roadmap.
  • •Deposits into Aave, Compound, Yearn, EigenLayer, and similar fixed-ratio lending or staking protocols are treated as transfers, not disposals — 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; pending NGNL legislation is expected to confirm the no-gain-no-loss treatment ChainTax applies today, but 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

See it on a real DeFi portfolio

I'll set up a demo with your most complex client type — every transaction sorted, every disposal with Show Working, full SA108 output.

Or email us directly at hello@chaintax.co.uk