UK crypto tax calculator with working you can check.

For the 2025/26 and 2026/27 tax years, crypto Capital Gains are taxed at a flat 18% (basic rate) or 24% (higher/additional rate), with no split-year adjustment. The annual exempt amount is £3,000, frozen across both years. 2024/25 was a split year: disposals before 30 October 2024 were taxed at 10%/20% and those from 30 October 2024 onwards at 18%/24%. ChainTax calculates the SA108 Box 51 split-year adjustment and shows the value for review.

HMRC requires you to pool acquisitions of the same asset and use the average cost as the cost basis for any disposal. ChainTax builds a Section 104 pool per asset, applies same-day matching first, then 30-day Bed & Breakfast, then S104 average cost, in HMRC's priority order. Every calculated disposal shows the matching rule used, the pool snapshot before and after the sale, and the price source.

On-chain: Ethereum, Arbitrum, Optimism, Base, and Polygon, using public wallet addresses only, never private keys or signing permissions. CSV import: 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. Solana, Avalanche and BSC are not yet covered on-chain. For those, manual entry or a Koinly CSV is the workaround.

Yes. Free for up to 200 transaction records account-wide, including classifications, review checks, and a preview of the report structure. Light is £49 for up to 2,500 account-wide transaction records and Active is £99 for up to 10,000. Each one-time purchase unlocks report access for its selected tax year; there is no subscription and calculation quality does not change by tier.

Each recognised disposal is matched against HMRC rules in the correct priority order (same-day → 30-day B&B → Section 104). 34 protocol-specific classifiers cover supported activity across Uniswap, Aave, Lido, Curve, GMX, Seaport, Treasure and others. Every transaction shows a confidence rating (High, Medium, Low). Anything we cannot recognise lands in a Needs Review queue rather than being presented as resolved.

You can review classifications, review checks, and the report structure before paying. Once you pay and download, refunds are available within 14 days under UK consumer law for unused purchases. Email hello@chaintax.co.uk to request a refund. Stripe processes the refund directly to your original payment method.

For the 2025/26 tax year (6 April 2025 to 5 April 2026), online Self Assessment is due by 31 January 2027 and paper returns by 31 October 2026. The 2024/25 deadlines (online 31 January 2026, paper 31 October 2025) have passed, though you can still file a late or amended return. SA108 is the supplementary capital gains page: for 2024/25 onwards, boxes 13.1–13.8 and Box 51 cover crypto disposals specifically.

Yes. Generate a shareable read-only link from the report. Your accountant can inspect recognised disposals, matching rules, the cost basis before and after each sale, and price-source confidence. No login is needed on their side. Once the material review checks pass, the PDF includes calculated SA108 box values for review.