Every classification rule, price source, and tax calculation explained. No black boxes — if you or your accountant want to verify a number, start here.
Every on-chain transaction is run through a deterministic priority chain of protocol-specific classifiers. The first matching rule wins. No machine learning, no guesswork — the same input always produces the same output.
| Protocol | Classification | Confidence |
|---|---|---|
| Coinbase CSV | Capital Gain | High |
| Binance CSV | Capital Gain | High |
| Kraken CSV | Capital Gain | High |
| Protocol | Classification | Confidence |
|---|---|---|
| Uniswap V2 & V3 | Capital Gain | High |
| Uniswap V1 | Capital Gain | High |
| 1inch V2–V6 | Capital Gain | High |
| Curve | Capital Gain | High |
| Mooniswap | Capital Gain | High |
| CoW Protocol | Capital Gain | High |
| Generic swap detection | Capital Gain | Medium |
| Protocol | Classification | Confidence |
|---|---|---|
| Lido | Capital Gain | High |
| Rocket Pool | Capital Gain | High |
| Coinbase cbETH | Capital Gain | High |
| Ethena | Transfer | High |
| Synthetix | Income | High |
| Atlas Mine | Income | High |
| Protocol | Classification | Confidence |
|---|---|---|
| Aave V1–V3 | Transfer | High |
| Protocol | Classification | Confidence |
|---|---|---|
| OpenSea Seaport 1.5/1.6 | Capital Gain | High |
| Treasure Trove | Capital Gain | High |
| Protocol | Classification | Confidence |
|---|---|---|
| Hop, Arbitrum, Optimism, Base, Polygon bridges | Transfer | High |
| WETH wrap/unwrap | Transfer | High |
| Fren Pet | Transfer | High |
| Realm | Transfer | High |
| Treasure Crafting | Transfer | High |
| ETH2 Beacon deposit | Transfer | High |
| Protocol | Classification | Confidence |
|---|---|---|
| Nexus Mutual | Capital Gain | High |
| Balancer V1 & V2 | Capital Gain | High |
| GMX | Capital Gain | High |
| Rhino.fi | Capital Gain | High |
| Gitcoin | Capital Gain | High |
| Compound V2 | Transfer | High |
| Protocol | Classification | Confidence |
|---|---|---|
| Pattern matching | Transfer | High |
| Generic swap heuristic | Capital Gain | Medium |
| AI fallback | Capital Gain | Low |
Centralised exchange transactions bypass the on-chain classification engine entirely. Upload a CSV and ChainTax handles the rest.
ChainTax sniffs the first 10 lines of your CSV to identify Coinbase, Binance, Kraken, or Koinly format automatically. No manual configuration needed.
Each exchange parser understands the source format — buys, sells, converts, rewards, fees. Events are created directly at high confidence without needing the on-chain engine.
Exchange trades feed into the same Section 104 cost basis pools as your on-chain activity. A Coinbase buy and a Uniswap swap of the same token share one pool — exactly as HMRC requires.
Three layers of dedup — within a CSV, across imports, and against existing data — prevent double-counting if you upload the same file twice or import overlapping date ranges.
Each classified transaction produces one of five event types. The tax treatment is determined by HMRC guidance, not by ChainTax.
| Type | Tax treatment | Examples |
|---|---|---|
| Capital Gain | Capital Gains Tax at 18% basic / 24% higher (from 30 Oct 2024) | Token swaps, sells, LP removals, liquid staking burns, NFT sales |
| Income | Income Tax at 20% / 40% / 45% | Staking rewards, LP fee collection, vesting claims, CRV rewards |
| Transfer | Non-taxable — no disposal occurs | Bridges, WETH wrap/unwrap, Aave supply/withdraw, game interactions |
| Liquidity | Adjusts your cost basis pool — no tax yet | LP deposits (tokens leave your pool, LP token enters) |
| Needs review | Flagged for you to check | Unrecognised contracts — you can edit the classification manually |
When you sell or swap a crypto asset, HMRC has strict rules for calculating your profit or loss. Most crypto tax tools get this wrong — especially the 30-day rule. ChainTax applies all three rules automatically in the correct order.
Acquisitions and disposals on the same calendar day are matched first. This prevents buying and selling the same asset on the same day to manipulate cost basis.
If you dispose of an asset and re-acquire the same asset within 30 days, the disposal is matched against that re-acquisition — not the Section 104 pool.
Remaining disposals draw from the Section 104 pool — an average cost basis across all acquisitions of that asset. HMRC does not permit FIFO or LIFO.
All dates use UK time (Europe/London) to correctly handle BST boundaries near tax year ends. Losses are carried forward and offset against future gains down to the annual exempt amount only (CRYPTO22800).
| Period | Basic rate | Higher rate | HMRC ref |
|---|---|---|---|
| From 30 Oct 2024 | 18% | 24% | Autumn Budget 2024 |
| Before 30 Oct 2024 | 10% | 20% | CRYPTO22100 |
Tax year 2024/25 is a split year — each disposal is taxed at the rate applicable on its disposal date. ChainTax checks every disposal against the 30 October 2024 boundary automatically.
2024/25 & 2025/26: £3,000
2023/24: £6,000
2022/23: £12,300
Gas fees (including L2 base fees on Optimism and Base) are treated as an HMRC allowable cost (CRYPTO22150), reducing your taxable gain per disposal.
Every token is priced in GBP at its transaction date. The oracle follows this waterfall — each step is tried only if the previous one has no data.
Every event carries a confidence level so you know exactly how much to trust each number.
All amounts decoded from on-chain logs and priced from cache or primary source.
Partial decoding or fallback price source used. Review recommended.
Unable to fully decode amounts. Oracle pricing may be skipped to avoid guessing.
Staking rewards (Lido stETH rebases, Synthetix fee claims) and LP fee collections (Uniswap V3) are classified as miscellaneous income at fair market value on the date received (CRYPTO40250). Income tax is applied progressively when you provide your salary: 20% basic / 40% higher / 45% additional. Without salary data, a flat rate is applied at your selected band.
Income events also enter the Section 104 acquisition pool at FMV — this means staking rewards you receive today affect your cost basis when you eventually sell that asset. DeFi income goes on SA100 (main return), not SA108.
From 2024/25, HMRC's SA108 form has dedicated crypto boxes (13.1–13.8) for the first time. ChainTax maps directly to every box — including the Box 51 split-year CGT rate adjustment that most tools miss.
| Box | Content | ChainTax source |
|---|---|---|
| 13.1 | Number of crypto disposals | Count of Capital Gain events |
| 13.2 | Total disposal proceeds | Sum of proceeds |
| 13.3 | Total allowable costs | Proceeds minus gain (HMRC-matched) |
| 13.4 | Total gains | Sum of positive gains |
| 13.5 | Total losses | Sum of negative gains (absolute) |
| 13.6 | Net gains or losses | 13.4 minus 13.5 (after loss offset) |
| 13.7 | Gains via real-time service | Usually zero |
| 13.8 | Tax paid on 13.7 | Usually zero |
| Box 51 | Split-year CGT rate adjustment | Gains split by 30 Oct 2024 boundary |
Unpriced disposals (where no market price was available) are excluded from all SA108 boxes and tracked separately. Read the full SA108 guide →
No tax tool is perfect. Here's what ChainTax cannot yet handle automatically — and what you should check manually or discuss with your accountant.
ChainTax is a tax calculation tool and does not provide financial, legal, or tax advice. The figures generated are estimates based on on-chain data and published HMRC guidance.
Always verify your figures with a qualified tax adviser before filing your Self Assessment return. ChainTax is not liable for any errors in your tax return.
Reference: HMRC Cryptoassets Manual (CRYPTO10000–CRYPTO45700)
Try our free transaction explainer to see how any on-chain transaction is classified. Or import your exchange trades and scan your wallets for a full HMRC-ready report.