Built to make complex UK crypto tax reviewable
ChainTax began with a real problem: a multi-year DeFi portfolio that could not be responsibly reduced to one unexplained tax number. The product classifies supported activity, reconstructs the UK calculation, and keeps evidence or judgement gaps visible.
Public addresses only. No private keys, signatures, or permission to move funds.
Same-day, 30-day and Section 104 matching are applied across your combined history.
Open the calculation to see proceeds, matched cost, fees, price evidence and pool movement.
Incomplete history, prices or unclear activity cannot quietly become a positive review state.
Production assurance · July 2026
A production-scale portfolio, rerun after every material engine change.
We re-run a large, multi-year DeFi portfolio after material tax-engine changes. Every movement must be explained, and unresolved evidence must remain visible. That assurance loop is part of the product. It is not a claim that complex crypto can be made risk-free.
See how the evidence gate works7,000+
portfolio events reprocessed
A large, multi-year DeFi portfolio was reclassified through the current engine.
Stable
classification result
Supported classifications did not move during the bounded assurance pass.
Explained
tax-year movement
The small net movement was traced to expected audit corrections, not unexplained drift.
Blocked
when evidence was incomplete
Low-confidence or incomplete evidence prevented a positive accountant-review state.
Anonymised internal assurance run. It demonstrates controlled behaviour and review boundaries; it is not customer-volume or filing-season evidence.
The problem
UK crypto tax becomes difficult when exchange exports, wallets and DeFi activity are incomplete or interpreted separately. A defensible result needs the full history, the correct UK matching order, and enough detail for the user or accountant to inspect the calculation.
Fragmented history
An omitted exchange, wallet or acquisition can change the shared Section 104 pool and every later disposal that uses it.
Multi-step DeFi
Bridges, LP positions, wrappers and staking can involve several linked legs. Unsupported or ambiguous activity needs visible review.
Thin evidence
A total without the matching rule, source value and pool movement is harder for a user or accountant to challenge and verify.
What makes ChainTax different
Not a US tool with UK settings. A UK tax engine, built from scratch.
Deterministic classifiers
34 protocol-specific classifiers cover supported LP positions, bridges, staking, and swaps by decoding contract interactions. Unresolved activity stays visible for review.
Show Working
Every calculated disposal shows how the stored figure was built: which HMRC matching rule was applied (same-day, B&B, or Section 104), the pool snapshot before and after, the price source, and the confidence level.
Box 51 + SA108
The 2024/25 tax year has two CGT rate regimes split at 30 October 2024. ChainTax automatically splits disposals at the boundary, computes Box 51, and fills SA108 boxes 13.1 through 13.8.
UK-native
Built exclusively for HMRC. Section 104 is the only cost-basis method, with same-day and bed-and-breakfast rules applied before the pool in the required order.
Charlie
Founder · ChainTax
The founder
Built from the portfolio that keeps testing the engine.
I am a UK DeFi investor and product engineer. I built ChainTax because fragmented exchange exports and multi-step on-chain activity made my own UK calculation difficult to inspect and explain. The founder portfolio remains an internal assurance case after material engine changes.
ChainTax Ltd is registered in Northern Ireland under company number NI739302.
Product proof, stated at the right level
These figures describe the current engine and its verification surface. They are not a substitute for customer adoption or filing-season evidence.
5,400+
Unit tests
Tax engine, detectors, pricing, API routes
34
Protocol detectors
Uniswap, Aave, Curve, Lido, Yearn, Convex, EigenLayer, Blur, Seaport NFTs, airdrops, and more
5
Chains
Ethereum, Polygon, Arbitrum, Optimism, Base
4
Native CSV parsers
Coinbase, Binance and Kraken; Crypto.com App (beta)
S104
Native pooling
The matching method HMRC requires
Box 51
Split-year CGT
The 2024/25 split-year rate change, auto-computed. 2025/26 and 2026/27 run a flat 18% / 24%.
Recorded code review; no public reviewer attestation or penetration-test report is published April 2026, covering auth, data access, payment flows, and concurrency-sensitive paths. Read the scope and limitations.
Decide from your own history.
Import exchange CSVs or connect a public wallet. ChainTax will show what it can support, what needs attention, and how each material figure was calculated.
200 transaction records free account-wide · Reports from £49 per tax year · No subscriptions ever