ChainTax methodology and coverage reference
The detailed reference for supported classification, UK matching, price evidence, calculations, report outputs, and known boundaries.
The product journey
Calculation and assurance are separate steps.
ChainTax can calculate supported activity while still blocking the report from a positive accountant-review state. That distinction prevents a technically finished sync from being presented as evidence-complete.
- 1
Import
Bring supported exchange CSVs and public wallet history into one account-wide dataset.
- 2
Classify
Protocol rules and transfer patterns create tax events with provenance and confidence.
- 3
Resolve
Material history gaps, low confidence, missing prices, stale matching, and filing inputs remain blocking checks.
- 4
Review
When those checks pass, inspect the totals, Show Working, frozen share link, PDF, and CSV evidence pack.
Positive readiness is a hard gate, not a confidence badge
A material low-confidence classification, incomplete source evidence, missing taxable price, required rematch, or unconfirmed filing input prevents “Ready for accountant review” from appearing.
Supported classification coverage
Supported on-chain transactions run through a deterministic priority chain of protocol-specific and pattern-based classifiers. Recognised rules produce repeatable output from the same normalised input. An optional AI suggestion can help a user investigate activity the rules did not match, but it is explicitly low-confidence, remains a review item, and cannot unlock positive readiness.
CSV imports
| Protocol or activity | Coverage | Classification | Confidence |
|---|---|---|---|
| CoinbaseBuy, sell, convert, earn, send and receive rows; missing GBP values lower confidence. | Automatic route available | Varies by row | Not stated |
| BinanceMulti-row trade reconstruction; missing GBP values lower confidence. | Automatic route available | Varies by row | Not stated |
| KrakenPaired trade rows and asset normalisation; missing GBP values lower confidence. | Automatic route available | Varies by row | Not stated |
| Crypto.com App (beta)Parser-tested App format; current real-export validation is still pending, so imported rows need review. | Automatic route with review | Varies by row | Not stated |
| Koinly universal CSVCompatible universal format; on-chain hashes enter the wallet pipeline. | Automatic route available | Varies by row | Not stated |
DEX / Swaps
| Protocol or activity | Coverage | Classification | Confidence |
|---|---|---|---|
| Uniswap V2 & V3Swaps, liquidity adds and removes, and fee collection. Unfamiliar methods or incomplete legs still need review. | Automatic route available | Disposal | |
| Uniswap V1 | Automatic route available | Disposal | |
| 1inch V2-V6 | Automatic route available | Disposal | |
| CurveSwaps plus CRV reward claims, which are treated as income when the evidence matches. | Automatic route available | Disposal | |
| MooniswapDirect 1inch AMM pool swaps. | Automatic route available | Disposal | |
| CoW ProtocolBatch-settled swaps on Ethereum and Base. | Automatic route available | Disposal | |
| Rhino.fiRecognised OTC trading calls. | Automatic route available | Disposal | |
| Rage TradeArbitrum perpetual-position and margin calls. Recognition does not settle the tax treatment of every derivative fact. | Automatic route with review | Transfer | |
| Generic swap detectionExactly one token out and one token in can be detected. A recognised pattern is not protocol-level evidence. | Automatic route with review | Disposal |
Staking / Yield
| Protocol or activity | Coverage | Classification | Confidence |
|---|---|---|---|
| LidostETH deposits, rebase income and wstETH wraps. Missing snapshots or incomplete wrap legs remain review items. | Automatic route with review | Disposal | |
| Rocket PoolrETH deposits and burns when the expected economic legs are present. | Automatic route available | Disposal | |
| Coinbase cbETH | Automatic route available | Disposal | |
| ether.fi, Renzo and KelpETH deposits, LST deposits, eETH rebases and eETH to weETH wraps. Incomplete legs and some basis carries need review. | Automatic route with review | Disposal | |
| EigenLayerLST strategy activity can carry basis when both legs are proved. Native ETH and incomplete receipt-token evidence need review. | Automatic route with review | Transfer | |
| StakeStoneRequest and settlement can occur in separate transactions, so ChainTax does not invent an automatic treatment. | Automatic route with review | Needs review | |
| SynthetixFee claims, vesting and synth exchanges when the expected evidence is present. | Automatic route available | Income | |
| Atlas MineMAGIC staking rewards and Bridgeworld Harvester activity. | Automatic route available | Income | |
| ConvexIncomplete deposit or withdrawal legs remain visible instead of receiving an automatic basis carry. | Automatic route with review | Transfer | |
| YearnBasis carries only when both the underlying and vault-share legs are proved. | Automatic route with review | Transfer | |
| EthenaStaking, sUSDe vault activity and sENA rewards. The exact economic legs determine whether basis can be carried. | Automatic route with review | Transfer |
Lending
| Protocol or activity | Coverage | Classification | Confidence |
|---|---|---|---|
| Aave V1-V3Decoded supply and withdrawal legs can carry basis; missing legs or unknown methods need review. Pre-6 April 2027 treatment is marked for professional review. | Automatic route with review | Transfer | |
| Compound V2Basis carries only when both the supplied asset and cToken share legs are proved. Legal treatment remains fact-specific. | Automatic route with review | Transfer |
NFT Marketplaces
| Protocol or activity | Coverage | Classification | Confidence |
|---|---|---|---|
| OpenSea Seaport 1.5/1.6NFT buys and sales on supported chains when order and payment evidence is complete. | Automatic route available | Disposal | |
| BlurEthereum marketplace fills with the expected order and transfer evidence. | Automatic route available | Disposal | |
| Treasure TroveArbitrum NFT marketplace trades paid in MAGIC. | Automatic route available | Disposal |
Bridges / Transfers
| Protocol or activity | Coverage | Classification | Confidence |
|---|---|---|---|
| Transfers between your own sourcesAdd every owned source and confirm ownership. A selector or label alone is not enough to infer a non-taxable transfer. | Automatic route with review | Transfer | |
| Supported same-owner bridgesDifferent assets, different owners or incomplete legs remain review items. | Automatic route with review | Transfer | |
| WETH wrap and unwrap | Automatic route available | Transfer | |
| Fren PetBase game staking, minting and accessory interactions. | Automatic route available | Transfer | |
| RealmTreasure DAO game interactions on Arbitrum. | Automatic route available | Transfer | |
| Treasure CraftingLegion summoning and related NFT game mechanics on Arbitrum. | Automatic route available | Transfer | |
| ETH2 Beacon deposit | Automatic route with review | Transfer |
Other
| Protocol or activity | Coverage | Classification | Confidence |
|---|---|---|---|
| PaxosNarrowly scoped to registered treasuries and Paxos-issued assets. | Automatic route available | Transfer | |
| Nexus Mutual | Automatic route available | Disposal | |
| Balancer V1 & V2Swaps and exits; joins are shown as liquidity events. | Automatic route available | Disposal | |
| GMXArbitrum swaps and positions. Recognition does not settle every derivative tax question. | Automatic route with review | Disposal | |
| GitcoinDonations are treated as disposals at market value. | Automatic route available | Disposal | |
| HolonymA proved free, non-transferable credential is treated as non-economic. Other movement is not guessed. | Automatic route with review | Transfer | |
| Named airdrop claimsRecognition identifies the receipt; eligibility work, services and other facts may still need review. | Automatic route with review | Income |
Fallbacks
| Protocol or activity | Coverage | Classification | Confidence |
|---|---|---|---|
| Pattern matchingApprovals, contract deployments, token transfers and other exact patterns. Pattern output can still require review. | Automatic route with review | Transfer | |
| Spam and unsolicited tokensThe label is evidence-scoped. Unfamiliar inbound activity is not silently assumed to be harmless. | Automatic route available | Transfer | |
| Optional AI suggestionA review aid for unmatched activity. It cannot unlock positive readiness. | Automatic route with review | Needs review |
Exchange CSV imports
Centralised exchange transactions bypass the on-chain classification engine entirely. Upload a recognised CSV, then review the imported rows and any missing-price or history checks.
Auto-detection
ChainTax sniffs the first 10 lines of your CSV to identify 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.
Pre-classified by parser
Each exchange parser understands the source format: buys, sells, converts, rewards and fees. Recognised rows are created without the on-chain engine; unsupported or incomplete rows still need review.
Shared S104 pools
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 account-wide pool under HMRC's asset-identification rules.
Deduplication
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.
Manual entries & overrides
You can review and correct classifications. Anything ChainTax got wrong can be edited, and activity the automatic engine missed can be added by hand with its provenance retained.
No chain pill on manual rows
Transactions imported from a CSV (or added by hand) have no blockchain, so the chain slot shows a short exchange tag instead: CB for Coinbase, BN for Binance, KR for Kraken, and CSV for Koinly.
The M marker
A teal M next to a type badge means you've edited the classification on that row. It's orthogonal to the confidence chip, so a high-confidence row you've overridden still shows its original chip.
Overrides win on re-sync
When you re-run auto-classification, any event you've edited is preserved, and ChainTax never overwrites your work. Reset an override from the row's edit panel if you want the automatic result back.
Tax event types
Each classified transaction produces one of five event types. These labels describe how the event enters the calculation; the correct legal treatment still depends on the facts, HMRC guidance, and the disclosed product choices below.
| Type | Tax treatment | Examples |
|---|---|---|
| Disposal | 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 in the calculation, as no disposal is recorded | Same-owner bridges, WETH wrap/unwrap, decoded Aave basis carries, game interactions |
| Liquidity | Disposal of the deposited tokens, so gains count toward Capital Gains Tax; the LP token enters your pool at market value | LP deposits (tokens leave your pool, LP token enters) |
| Needs review | Flagged for you to check | Unrecognised contracts, which you can edit the classification of manually |
HMRC matching rules
When you sell or swap a crypto asset, HMRC has strict rules for calculating your profit or loss. ChainTax applies all three rules automatically in the required order and exposes the selected match on each disposal. See them applied to your own transactions in the UK crypto tax calculator.
1. Same-day rule
CRYPTO22252Acquisitions 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.
2. 30-day B&B rule
CRYPTO22253If 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.
3. Section 104 pool
CRYPTO22251Remaining 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 (TCGA 1992).
Capital gains tax rates
| 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, so each disposal is taxed at the rate applicable on its disposal date. ChainTax checks every disposal against the 30 October 2024 boundary automatically. For 2025/26 and 2026/27 the 18%/24% rates apply to the whole year, and only 2024/25 needed a split-year (Box 51) adjustment.
Annual exempt amount
2024/25, 2025/26 & 2026/27: £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.
How prices are sourced
ChainTax attempts to price each supported asset in GBP at its transaction date. The oracle follows this waterfall, and a missing taxable price remains visible rather than being written as zero.
- 1Price cache: Previously fetched prices are stored to avoid redundant API calls.
- 2Kraken: GBP-native daily closes for supported major assets, avoiding an FX conversion step where possible.
- 3DefiLlama: Free historical token prices in USD, converted to GBP using Frankfurter.app with ECB fallback. FX rates are validated within a 0.6–1.6 sanity range.
- 4CoinGecko: Fallback when DefiLlama has no data for a token. Uses the CoinGecko historical API.
- 5Visible gap: If no price is available from any source, the event is flagged for review. Other priced events can still calculate, but a material taxable gap blocks positive review.
Confidence levels
Classified events carry a confidence level so you can see which results deserve closer review.
All amounts decoded from on-chain logs and priced from cache or primary source.
Partial decoding or fallback price source used. Worth a quick check.
Unable to fully decode amounts. Oracle pricing may be skipped to avoid guessing.
DeFi income treatment
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 (CRYPTO21200). 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.
When your salary plus DeFi income crosses a band boundary, the calculation splits the income across both bands automatically. Verify the band breakdown if you're close to a boundary.
Income events also enter the Section 104 acquisition pool at FMV, which 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.
SA108 mapping
From 2024/25, HMRC's SA108 form has dedicated crypto boxes (13.1–13.8) for the first time. ChainTax calculates the applicable crypto box values, including the Box 51 split-year CGT rate adjustment, for review.
| Box | Content | ChainTax source |
|---|---|---|
| 13.1 | Number of crypto disposals | Count of Disposal 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 →
Your reconstructed tax pools
A report is a snapshot of one tax year. Alongside it, ChainTax values the balances implied by your imported transaction history against the same Section 104 cost basis your report uses, so the two reconcile. Sign in and open Holdings to see your own.
Market value vs. cost basis
Where a current GBP price is available, the reconstructed token pool is valued against its Section 104 pooled cost. Holdings without a supported current price remain visibly unpriced.
Tokens and NFTs together
Fungible tokens are valued live; NFTs are listed at their recorded cost basis only. ChainTax does not invent a floor price it can’t verify. A holding with no current market price is shown honestly as unpriced, not counted as a loss.
History builds forward
A daily snapshot records your portfolio value and cost basis from the day you start, and there is no invented back-history. The chart is honest about having little to show on day one and fills in as the days pass.
Export and share
Export your holdings to CSV, or hand your accountant a read-only, frozen snapshot via a revocable share link, the same sharing model as your report.
This is a tax-pool view, not an independent wallet-balance reconciliation, tax advice, or a filing.
Simulating a disposal
From your Holdings page you can model a hypothetical “what-if” disposal and see how selling some of a holding today would change your Capital Gains Tax position for the current tax year. It is a calculator you choose to run. Nothing is saved, nothing is filed, and ChainTax never tells you whether to buy or sell.
What it does
You pick an amount of a token you still hold. ChainTax estimates the proceeds at today’s price, works out the gain or loss, and shows the marginal effect on your current-year CGT and how much of your tax-free allowance it would use.
How the number is produced
The hypothetical sale is appended to your real Section 104 pools and run through the same HMRC matching your report uses: same-day, then the 30-day bed & breakfast rule, then the Section 104 pool. Because a today-dated disposal is chronologically last, it slots in after everything you have already done rather than reshuffling how your existing transactions were matched.
Where the data comes from
Units come from your synced holdings; the price is the latest available GBP price from the same oracle used across ChainTax (cache → Kraken → DefiLlama → CoinGecko). If a token has no current price it can’t be simulated.
What it is not
It is not advice, and it is not a filing. Figures are estimates that assume the disposal happens now at the shown price. Actual results depend on the real disposal date, price, and fees. Modelling the current tax year uses figures from an unlocked report for that year.
Before you act on a simulation
A simulation is a calculation tool, not tax or financial advice. Whether to dispose of an asset, and any timing around the 30-day bed & breakfast rule, is a decision for you and a qualified tax adviser. ChainTax does not recommend disposals and does not receive anything if you make one.
Important boundaries and manual checks
These are calculation boundaries, current-law choices, and coverage gaps to review before relying on a report.
- •stETH rebases: ChainTax estimates rebase income from periodic wallet-balance snapshots (monthly and at tax-year boundaries), net of transfers, then values the increase on the snapshot date. This covers every fully synced Ethereum wallet on the account, but it is not a daily receipt-by-receipt reconstruction.
- •Receipt-token deposits: For supported Aave, Compound V2, Yearn, and Convex actions, ChainTax currently treats decoded deposits and withdrawals as transfers and carries Section 104 basis when both economic legs are present. Missing required legs are sent to Needs review. EigenLayer automation covers StrategyManager LST restaking, not native-ETH EigenPod restaking. HMRC's current CRYPTO61620 treatment depends on beneficial ownership and can treat a token exchange as a disposal. Draft NGNL rules were published on 13 July 2026 for qualifying arrangements from 6 April 2027, but are not yet law. Ask a tax adviser before changing current-period treatment.
- •Internal ETH returns: Known Rocket Pool and cbETH methods use trace data to recover ETH returned through internal calls; if that data is unavailable, the event stays in Needs review. Nexus Mutual sales can instead use the NXM market value as a fallback, and the event note says when that happened.
- •Chain coverage: Automatic on-chain sync supports Ethereum, Arbitrum, Optimism, Base, and Polygon. Other networks, including Solana and Avalanche, need a supported CSV import or manual records.
Disclaimer
ChainTax is a tax calculation tool and does not provide financial, legal, or tax advice. The figures generated are estimates based on imported and on-chain data, published HMRC guidance, and the evidence available in the account.
Always verify your figures with a qualified tax adviser before filing your Self Assessment return. Every calculated disposal shows its working so they can check each number line by line.
Reference: HMRC Cryptoassets Manual (CRYPTO10000–CRYPTO100000)
Want the shorter product journey?
See how ChainTax moves from imported history to reviewable working, or test it on up to 200 transactions without paying.