Crypto tax software is not wrong because the maths is wrong. It is wrong because it is guessing. Every tool has to infer what an unlabelled on-chain movement was, what a token was worth in sterling at 14:03 on a Tuesday, and what happened on an exchange that no longer exists. When it guesses badly, the result is almost always a gain that is far too high, and the taxpayer files it because the report looks authoritative.
This page is an honest account of where the line sits. If you bought on one exchange, held, and sold, a £50 subscription will do the job and you do not need us. If any of the eight failure modes below apply to you, no subscription will fix it, because the problem is upstream of the calculation.
Where the number actually goes wrong
| Failure mode | What it does to your figure | Fixable in software? |
|---|---|---|
| Unlabelled internal transfers. Moving coins between your own wallets is not a disposal, but an untagged withdrawal followed by an untagged deposit looks like a sale and a purchase | Inflates proceeds and gains, often by an order of magnitude | Only if you can identify and tag every leg |
| Missing cost basis. Coins arriving from a delisted exchange, a closed account or a pre-2018 wallet with no import | Cost basis defaults to zero, so the entire proceeds become gain | No — the data does not exist to import |
| Dead and delisted exchanges. FTX, Celsius, BlockFi, Cryptopia, historic UK platforms | Whole periods of history absent; opening pool unknown | No |
| Wrong sterling valuation on swaps. Thin liquidity pairs, illiquid tokens, or a USD price converted at the wrong daily rate | Skews every swap in the chain, compounding | Partially, with manual overrides |
| Income versus capital characterisation. Staking rewards, mining, airdrops, liquidity provision and lending returns are income on receipt and then acquire a base cost | Double counts or omits; wrong tax entirely, not just the wrong amount | No — it is a judgement, not a data field |
| DeFi position mechanics. Whether depositing into a pool is a disposal of the deposited tokens turns on beneficial ownership, not on the transaction hash | Can create or erase very large gains | No — tools apply a blanket assumption |
| The wrong jurisdiction method. A tool set to FIFO or to US wallet-by-wallet basis rather than UK section 104 pooling with same-day and 30-day matching | Systematically wrong in every year | Yes, if you notice the setting |
| Fees and non-allowable costs. Fiat deposit and withdrawal fees are not allowable; fees paid in tokens are themselves disposals | Small individually, material over thousands of transactions | Rarely handled correctly |
Notice the pattern. Two of the eight are settings. Six are missing information or judgement calls, and no amount of software solves either.
When software on its own is enough
We would rather tell you this than sell you something you do not need. A subscription alone is usually sufficient if all of the following are true:
- You used one or two major centralised exchanges with complete API history.
- You bought with fiat, held, and sold. No DeFi, no bridging, no self-custody movement you cannot account for.
- Your transaction count is in the hundreds, not the tens of thousands.
- No staking, mining, airdrops, NFTs, lending, liquidity provision or margin.
- Nothing was lost, stolen, or stranded on a failed platform.
- You have been UK resident throughout and have no cross-border complication.
Run it through our free UK crypto CGT calculator as a sense check, file it, and get on with your life.
How the main tools differ on the UK rules
All of the widely used tools can produce a UK computation. Where they differ is how much reconstruction they expect you to do first, and how they behave when data is missing.
| Tool | UK positioning | Where users most often come unstuck |
|---|---|---|
| Koinly | The most widely used tool for UK reporting, with section 104 pooling and same-day and 30-day matching built in | Untagged internal transfers and zero-cost-basis warnings that get ignored rather than resolved |
| Recap | UK-built and UK-first, with strong HMRC-shaped reporting | Smaller integration coverage for long-tail chains and exotic protocols |
| CoinTracking | Very deep history and format support, heavily configurable | The configurability itself — a wrong global method setting silently affects every year |
| CoinTracker, CoinLedger, ZenLedger, TokenTax | Primarily US-oriented, with UK method options | Defaults that assume US basis tracking rather than UK pooling |
| Blockpit | Strong European coverage, multiple national methods | Jurisdiction selection and residency-change handling |
| BittyTax | Open source, UK-specific, precise and auditable | Command-line and manual data preparation; not for casual users |
We work with output from all of them. We do not resell any of them and we have no affiliate arrangement with any vendor, which is why we are comfortable telling you when the tool is fine and the problem is the data.
What an accountant adds that no tool can
- Reconstruction. Rebuilding history from on-chain data, bank records, counterparty evidence and surviving exports when the exchange has gone. See transaction analysis and reconciliation.
- Characterisation. Deciding, and being able to defend, whether a receipt is income or capital, whether activity amounts to a trade, and whether a DeFi deposit was a disposal.
- Reliefs a tool will never claim for you. Negligible value claims on worthless or stolen tokens, loss claims, and the interaction with other income.
- A defensible methodology. Where records are genuinely unavailable, HMRC accepts a just and reasonable basis, but only if the basis is documented and consistently applied. Software output is not a methodology.
- Standing between you and HMRC. If a nudge letter or enquiry arrives, someone has to explain the figures, and a subscription cannot.
Does using tax software protect me if HMRC disagrees?
Partly, and it is worth understanding how. Penalties under Schedule 24 FA 2007 depend on behaviour, and the behaviour bands run from reasonable care through careless to deliberate, with the assessing window running from four years to twenty accordingly.
Using a recognised tool, retaining the exports, and keeping a record of the settings and assumptions is genuine evidence that you took reasonable care. It does not make an incorrect return correct, but it can be the difference between a nil penalty and one at 70%. Ignoring the tool's own zero-cost-basis and missing-data warnings cuts the other way, because the software told you and you filed anyway.
Frequently asked questions
Do I need an accountant if I already use Koinly?
Not necessarily. If your history is complete, came from one or two major exchanges, and involves no staking, DeFi, NFTs, lost coins or cross-border complication, the software output is likely sound. If the tool is showing missing cost basis warnings, unmatched transfers, or you have activity it had to guess at, the output needs reconciling before it is filed.
Why is my Koinly or Recap gain so much higher than I expected?
Almost always unlabelled internal transfers being read as disposals, or missing cost basis defaulting to zero so the whole proceeds figure becomes gain. Both inflate the number dramatically and both are fixable, but only by identifying the underlying movements rather than by changing a setting.
Which crypto tax software is best for the UK?
For most UK investors Koinly and Recap are the strongest starting points, because both implement section 104 pooling with same-day and 30-day matching natively. BittyTax is excellent and precise if you are technical. US-first tools can produce UK figures but need their method setting checked carefully. The best tool is the one whose integrations actually cover the platforms you used.
Can you fix my existing software report rather than starting again?
Yes, and that is usually cheaper. We take your export, identify where the data is incomplete or mislabelled, resolve what can be resolved and document a defensible basis for what cannot, then rebuild the computation. Starting from scratch is rarely necessary.
Does HMRC accept crypto tax software reports?
HMRC does not approve or endorse any particular tool. What it assesses is whether the figures on the return are correct and whether reasonable care was taken. A software report is evidence of care, not a substitute for accuracy.
Is a spreadsheet good enough?
For a small number of transactions in a single token, yes, provided you apply the same-day rule, the 30-day rule and section 104 pooling in the correct order. Beyond a few dozen transactions, or across several tokens, manual pooling becomes unreliable very quickly, which is exactly the point at which the 30-day rule starts silently changing answers.
What if the exchange I used no longer exists?
This is common and it is solvable. We reconstruct from on-chain data, bank statements showing fiat on and off ramps, surviving partial exports, email confirmations and counterparty records, then document the assumptions used to bridge the gaps. HMRC accepts a just and reasonable basis where records are genuinely unavailable.
How much does it cost to have a crypto computation reviewed?
It depends on transaction volume, the number of platforms involved and how much of the history survives. We scope it first and agree a fixed fee before starting, so you know the cost before you commit rather than after.
This page is general guidance on UK tax law as at 10 August 2026 and is not advice for any particular case. Product names are the trade marks of their respective owners; we have no commercial relationship with, and receive no commission from, any of the tools mentioned. HMRC's internal manuals are guidance for HMRC staff, are not law, and do not bind HMRC in an individual case. Reviewed by the TaxDigit crypto tax team. Updated August 2026.
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