If you use Koinly, Recap or another crypto tax software platform to calculate your UK crypto taxes, it is important to check your crypto tax report before using the figures on your tax return.
For straightforward crypto investors there may be relatively little to check. However, things can become considerably more complicated if you have used several exchanges or wallets, traded over several years, received staking rewards or become involved with DeFi.
We have been helping clients with UK crypto tax since 2017. When we first started supporting clients in the crypto space, there were very few specialist crypto tax software providers. Calculating gains could also involve reconstructing years of exchange and wallet records before applying the UK’s tax rules.
The software available today is considerably more effective, and we regularly use specialist crypto tax software ourselves.
However, one principle has not changed:
Your crypto tax calculation is only as reliable as the records and transaction information behind it.
Missing wallets, incomplete exchange histories, incorrectly identified transfers, missing acquisition costs and complex DeFi transactions can all affect the final calculation.
In this guide, we explain what to check on your crypto tax report before filing with HMRC. We also look at some of the problems we regularly encounter and explain how you can investigate them.
Why Crypto Tax Software Reports Still Need Checking
Specialist crypto tax software has transformed the preparation of crypto tax calculations.
For a crypto investor with thousands of transactions across multiple exchanges, wallets and blockchains, attempting to reconstruct and calculate everything manually would be extremely time-consuming. In many cases, it would simply be impractical.
Our default approach is to use specialist crypto tax software when preparing and reviewing our clients' calculations. The software can process large transaction histories, convert transactions into sterling and apply the UK’s share matching and pooling rules far more efficiently than a manual calculation.
However, the reliability of the final report still depends on the quality and completeness of the underlying data. In more complex cases, it also depends on correctly understanding what the transactions actually represent.
From our experience, problems tend to fall into three broad areas.
Incomplete transaction data
An exchange, wallet, blockchain or part of the historical transaction record may be missing.
This matters particularly where the missing information relates to the original acquisition of assets later moved between several wallets or exchanges.
Incorrectly identified or classified transactions
The transaction may be present, but the software may not have enough information to determine exactly what happened.
For example, a withdrawal from an exchange could represent a transfer to the investor's own wallet rather than a disposal. If the receiving wallet is missing, the software can only analyse one side of the transaction.
Transactions requiring tax interpretation
This becomes increasingly important with more complex crypto activity.
DeFi lending, liquidity pools, staking, wrapping, bridging and other smart-contract interactions can involve several token movements. However, those movements may form part of a single economic arrangement.
The tax treatment may depend upon matters such as what assets were received in return, whether beneficial ownership changed and the precise nature of the arrangement.
Therefore, understanding the underlying crypto activity can be just as important as understanding the tax rules.
Specialist software performs an essential part of the calculation. However, it doesn’t remove the need to review the information behind it.
The objective isn’t simply to establish whether the software has performed the calculations correctly. You also need to establish whether it has the right transactions, whether those transactions have been interpreted correctly and whether the resulting treatment reflects UK tax law.
Common Issues to Check on Your Crypto Tax Report
When reviewing a crypto tax report, it is important not to look at individual warnings or transactions in isolation. Sometimes a problem with one transaction originates much earlier in the transaction history.
For example, a missing exchange or wallet can lead to unmatched transfers, missing acquisition costs and incorrect balances elsewhere in the report
With that in mind, the following are some of the issues we regularly encounter and the practical steps you can take to resolve them.
Your Crypto Tax Report Shows Missing Purchase History
One of the most common issues we see in crypto tax reports is missing acquisition history.
This usually happens when the software can identify a disposal but cannot establish when you originally acquired the crypto or what it cost.
For example, suppose your report shows that you disposed of 2 ETH for £6,000, but the software has no record of how those ETH originally entered your portfolio.
The issue may not be with the disposal itself. Instead, the missing information could relate to a transaction several years earlier on an exchange or wallet that was never imported.
A typical history might look like this:
| Stage | What happened | What the tax software may see |
|---|---|---|
| 1 | You bought 2 ETH on Exchange A for £2,000 | Missing if Exchange A was never imported |
| 2 | You transferred the ETH to your private wallet | May appear only as an incoming transfer |
| 3 | You later moved the ETH to another wallet | Usually identifiable if both wallets are included |
| 4 | You transferred the ETH to Exchange B | May be matched as a transfer |
| 5 | You sold the 2 ETH for £6,000 | Disposal is visible |
| Result | The sale is recorded, but the original £2,000 acquisition may be missing | The report may show an incorrect or nil acquisition cost |
This is why simply reviewing transactions for the current tax year is not always enough.
For UK Capital Gains Tax purposes, cryptoassets such as ETH are generally subject to the UK's share matching and pooling rules. As a result, the allowable cost of a disposal today may depend on purchases made several years earlier.
If part of that historic transaction record is missing, the software may not have enough information to calculate the gain correctly.
How to investigate missing purchase history
If your report shows a missing purchase history or a zero acquisition cost, don't automatically assume that the asset genuinely cost nothing.
Instead, trace the asset backwards through your transaction history.
Check older exchange accounts and private wallets, historic CSV files, transaction confirmations, bank records, blockchain transaction hashes and previous crypto tax reports.
Often, an apparent missing acquisition cost is actually a missing part of the transaction history.
Once you find and import the earlier records, the software may reconnect the chain of transactions. It may then be able to calculate the gain using the correct acquisition history.
Therefore, investigate a missing purchase history warning wherever possible rather than simply accepting a nil cost.
A Wallet or Exchange Is Missing
Another common issue is discovering that an exchange, wallet or blockchain used in earlier years hasn't been included in the crypto tax calculation.
This might be an old exchange account that is no longer used, a hardware or mobile wallet, or simply a blockchain address that hasn't been imported into the software.
Importantly, one missing source can affect transactions elsewhere in the report.
Suppose you bought ETH on an exchange several years ago, withdrew it to a private wallet and later transferred it to another exchange. If the original exchange history is missing, the software may see the ETH arriving but have no record of what you originally paid for it.
Alternatively, the exchange history may be present while the private wallet is missing. In that case, withdrawals and deposits that were actually transfers between your own accounts may remain unmatched.
A number of apparently unrelated warnings can therefore have the same underlying cause: part of the transaction history is missing.
How to find what's missing
Start by listing every exchange and wallet you have used, including historic accounts that are now empty. Then compare your list with the sources imported into your crypto tax software.
If something is missing, check old exchange accounts, wallet addresses, CSV files, bank records, transaction histories and previous crypto tax reports to see whether the missing history can be recovered.
Where possible, import the missing source before manually correcting individual transactions. What appears to be dozens of separate problems may resolve once you add the missing exchange or wallet.
In other words, several apparent errors can sometimes be traced back to one missing part of the transaction history.
A Transfer Between Your Own Wallets Is Showing as a Disposal
Moving crypto between exchanges and wallets that you own is a normal part of managing a crypto portfolio.
For example, you might buy Bitcoin on Kraken and later transfer it to a Ledger hardware wallet for safekeeping.
Where you remain the beneficial owner of the Bitcoin throughout, simply moving it from one wallet or account to another would not normally constitute a disposal for Capital Gains Tax purposes.
However, problems can arise when the software can see only one side of the transfer.
Suppose you withdraw 1 BTC from Kraken to your Ledger wallet.
If you have imported Kraken but not the Ledger wallet, the software can see the Bitcoin leaving. It may not, however, know that the destination wallet also belongs to you.
| Stage | What actually happened | What the tax software may see |
|---|---|---|
| 1 | You hold 1 BTC on Kraken | 1 BTC held on Kraken |
| 2 | You withdraw 1 BTC from Kraken | 1 BTC leaves Kraken |
| 3 | The 1 BTC arrives in your Ledger wallet | Missing if the Ledger wallet hasn't been imported |
| Result | You still own the 1 BTC. It has simply moved from Kraken to your Ledger wallet. | The software may show an unmatched withdrawal or potentially classify the transaction incorrectly because it cannot see the destination. |
This is an important distinction. A blockchain transaction may show that Bitcoin moved to another address, but it doesn’t tell the tax software that you own that address.
How to check an unmatched transfer
First, establish whether you owned both the sending and receiving accounts or wallets.
Next, make sure both sides of the transaction appear in your crypto tax software. The transaction hash, wallet addresses, date, quantity and any fees can help you match the movements.
If the receiving wallet hasn’t been imported, adding its address or transaction history may allow the software to identify the transfer correctly.
You can then check whether the withdrawal and corresponding receipt have been matched as the same transaction.
However, don’t simply change every unexplained withdrawal into a transfer between your own wallets.
An unexplained withdrawal could instead represent a payment, gift or another transaction with different tax consequences. Therefore, make sure you have sufficient evidence that the destination wallet belonged to you.
The aim is to identify and match both sides of the transaction, not simply change the tax treatment of an unexplained withdrawal.
Your Crypto Balances Don’t Reconcile
One of the most useful checks you can perform on a crypto tax calculation is to compare what the software says you hold with what you actually hold.
Suppose your crypto tax software shows a closing balance of:
| Comparison | BTC |
|---|---|
| Balance shown by crypto tax software | 3.25 BTC |
| Actual balance across exchanges and wallets | 4.25 BTC |
| Difference to investigate | 1.00 BTC |
A difference of 1 BTC doesn’t necessarily mean the tax calculation is wrong. However, you should understand the reason before relying on the report.
The discrepancy might result from a missing transaction or wallet. Alternatively, an API may have imported an incomplete history, overlapping CSV and API imports may have created duplicates, or the software may have failed to match a transfer.
How to investigate a balance difference
Start by comparing the balance shown in the tax software with the assets actually held across your exchanges and wallets at the relevant date.
If they don’t agree, investigate the cause rather than inserting a manual transaction simply to make the numbers match.
Check whether all exchanges and wallets are included, whether APIs cover the complete period and whether CSV imports overlap with API data. Also look for unmatched transfers, incorrect classifications and inaccurate opening balances.
For larger portfolios, focus initially on the most significant assets and discrepancies. There may be little value in investigating every immaterial difference before addressing the larger ones.
This is essentially the crypto equivalent of a bank reconciliation.
If a company’s accounting records showed £50,000 in the bank but its bank statement showed £70,000, an accountant wouldn’t simply insert £20,000. Instead, they would investigate why the figures differ.
The same principle applies to crypto.
A reconciliation difference isn’t something to hide. Instead, treat it as a clue to the underlying problem.
Crypto-to-Crypto Trades Haven’t Been Treated as Disposals
Another important area to check is whether exchanges of one cryptoasset for another have been treated correctly.
A common misconception is that Capital Gains Tax only becomes relevant when crypto is sold for pounds and the money is withdrawn to a bank account.
However, that is not generally the case.
For UK Capital Gains Tax purposes, exchanging one crypto for another will normally involve a disposal of the crypto you give up.
For example, suppose you originally bought 0.5 BTC for £10,000. Later, when the Bitcoin is worth £25,000, you exchange the entire 0.5 BTC for ETH.
No pounds have been received, but there has still potentially been a disposal of the Bitcoin.
| Transaction | Amount |
|---|---|
| Original cost of 0.5 BTC | £10,000 |
| Market value when exchanged for ETH | £25,000 |
| Illustrative gain before other costs and CGT rules | £15,000 |
The ETH received will also have an acquisition value for future Capital Gains Tax purposes, broadly based on its sterling market value when acquired.
Consequently, a crypto-to-crypto trade can potentially crystallise a taxable gain even though you haven’t received cash to pay the resulting tax.
The example is deliberately simplified. In practice, you cannot necessarily calculate the gain by simply deducting the original purchase price from the disposal proceeds. UK cryptoassets are generally subject to the Capital Gains Tax share matching and pooling rules.
What to check
Check that your transaction history includes exchanges between different cryptoassets, rather than looking only for transactions involving GBP.
This is particularly important if you have used multiple centralised or decentralised exchanges, trading bots or older platforms with separately imported histories.
If one cryptoasset leaves your portfolio and another appears, establish what actually happened. Was it a trade, a transfer between your own wallets, a DeFi transaction or something else?
The distinction matters because the tax consequences can be very different.
Also consider earlier years. A portfolio may have generated significant gains through crypto-to-crypto trades long before any money reached a bank account.
Receiving pounds into your bank account isn’t what determines whether a crypto disposal has taken place.
Staking and Other Crypto Rewards Have Been Classified Incorrectly
Staking rewards need particular attention. Here, the problem may not be whether the software captured the transaction, but whether it applied the correct tax treatment.
Depending on the circumstances, cryptoassets received from staking can be taxable as income when received. The sterling value at that point can then become relevant to the Capital Gains Tax calculation when you eventually dispose of the tokens.
As a result, the same cryptoassets can potentially create two separate tax considerations at different times.
For example, suppose you receive staking rewards worth £1,000 and later dispose of those tokens when they are worth £1,600:
| Stage | What happens | Potential tax treatment |
|---|---|---|
| 1 | You receive staking rewards worth £1,000 | The £1,000 may be taxable as income |
| 2 | You continue to hold the tokens | The value already recognised may form part of the acquisition cost for CGT purposes |
| 3 | You later dispose of the tokens for £1,600 | There may be a further £600 capital gain, subject to the normal CGT rules |
| Overall | £1,000 received as a reward and £600 subsequent increase in value | Potential Income Tax on the reward followed by CGT on the subsequent increase in value |
This is a simplified example, but it demonstrates why the eventual disposal shouldn't be considered in isolation.
If the original reward is missing or incorrectly classified, it could affect both the earlier income calculation and the later CGT position.
How to review staking rewards
Review transactions where crypto has entered your portfolio without an obvious corresponding purchase.
For each one, establish why you received the tokens, when you became entitled to them and their sterling value at that time. Then check how the software classified the receipt and any later disposal.
This isn’t limited to conventional staking. Similar questions can arise with other rewards and crypto receipts. Ultimately, the correct treatment depends on why and in what circumstances you received the tokens.
Manually changing a classification simply to remove a warning can also create problems elsewhere.
For example, treating a genuine reward as a transfer might remove an apparent discrepancy. However, it could also remove taxable income and leave the subsequent acquisition history incorrect.
Understanding why you received the crypto is often just as important as knowing how much you received.
DeFi Transactions Need More Than an Automated Classification
DeFi is where reviewing a crypto tax report can become considerably more technical.
Activities such as lending, liquidity pools, staking, wrapping and bridging can involve several movements of crypto and interactions with smart contracts. Although the software may accurately record those movements, that doesn’t necessarily determine their UK tax treatment.
The important question is what actually happened to the assets.
For example, depositing crypto into a protocol while retaining beneficial ownership may have different tax consequences from transferring beneficial ownership in return for a new token representing your interest in the arrangement.
Therefore, two transactions that look similar on the blockchain can have different tax consequences.
What to check with DeFi transactions
Before changing classifications, establish the nature of the arrangement. Consider what you transferred, what you received in return, whether beneficial ownership changed and what happened when you exited.
Where necessary, use the transaction history and protocol documentation to understand what happened. Only then can you consider the individual movements under the appropriate UK tax rules.
This is an area where specialist tax advice can be particularly valuable.
A tidy-looking crypto tax report isn’t necessarily correct if nobody has properly understood the underlying DeFi transactions.
You can read more about the proposed changes affecting the tax treatment of crypto DeFi platforms here.
Check Which Crypto Tax Rules Apply
Crypto tax rules continue to develop. Therefore, you also need to consider which rules applied when the transaction took place.
This is particularly relevant to crypto lending, liquidity pools and stablecoins, where significant changes are proposed from April 2027.
For certain qualifying crypto lending and liquidity-pool arrangements, draft legislation proposes broadly introducing no gain, no loss treatment. The intention is to prevent a Capital Gains Tax charge simply because cryptoassets enter a qualifying arrangement. Instead, the tax consequences would generally be deferred until an economic disposal occurs.
Changes are also proposed for qualifying stablecoins. From April 2027, disposals by individuals and trustees would be exempt from Capital Gains Tax, while certain interest-like returns could instead fall within the savings income rules.
How to Deal With Changing Crypto Tax Rules
Make sure your records allow you to establish what the transaction was and when it took place.
For more complicated lending or liquidity-pool arrangements, also retain enough information to show what you transferred, what you received and how the arrangement operated.
You can then consider the transaction under the rules applying to the relevant tax year.
This matters particularly when legislation is changing because apparently similar transactions may fall under different rules depending on when they occurred.
Your crypto tax software may accurately record the date, value and movement of the assets. However, you still need to establish which UK tax rules apply.
Don’t assume that the treatment applied in an earlier tax year will necessarily apply to a similar transaction undertaken later.
What Can a Crypto Tax Specialist Do – and What Remains Your Responsibility?
There is an important distinction between using a generic accountant who occasionally deals with crypto and working with an adviser who has specialist knowledge of UK crypto taxation.
As the examples above show, reviewing a crypto tax calculation involves much more than taking the capital gain from a software report and entering it on a tax return.
A specialist may need to investigate transaction histories, reconcile exchanges and wallets and understand what happened on-chain. They then need to apply the correct UK tax treatment.
The software helps calculate the numbers. Specialist tax knowledge helps determine whether those are the right numbers to report.
However, there are practical limits to what any adviser can do.
What If Your Historic Crypto Records Are Missing?
Suppose 5 ETH arrived in your wallet in 2021 from an exchange you previously used.
The blockchain may allow you to trace the transfer. However, if the exchange account has closed and its records are unavailable, you may not be able to establish the original acquisition history.
For example, you may no longer know what you paid for the ETH or what trading took place before you withdrew it.
This is particularly relevant to centralised exchanges. The blockchain can show assets entering or leaving an exchange, but it doesn't necessarily provide a record of trades that took place within the exchange itself.
An experienced crypto tax specialist can often investigate missing transactions, trace transfers and reconstruct complicated histories from the evidence that remains.
Where records are incomplete, start with what you can establish and work systematically from there. Other exchanges, wallets, blockchain records, bank transactions and previous tax reports may help fill the gaps.
However, don’t insert arbitrary transactions simply to remove software warnings or force balances to agree. Doing so may make the report look complete without establishing what actually happened.
But there is an important difference between reconstructing a transaction history from available evidence and creating evidence that no longer exists.
Neither crypto tax software, blockchain analysis nor specialist tax expertise can manufacture records that are no longer available.
Crypto Record Keeping: What Should You Keep?
Good record keeping is particularly important with crypto. Ultimately, you remain responsible for maintaining the records that support your tax position, even if you use crypto tax software or appoint a specialist adviser.
There is also a practical reason to keep those records as you go along.
Crypto exchanges can close, merge or change their reporting systems. Accounts can also become inaccessible, while APIs may not provide the same historical information several years later.
Consequently, recovering a complete transaction history five years after the event can be much harder than retaining it today.
What Records Should You Retain?
As a starting point, periodically download and securely retain the complete transaction history from exchanges you use rather than relying upon being able to access it indefinitely.
In addition, keep enough information to understand your wider transaction history. This may include exchange statements, wallet addresses and transaction hashes, records of staking or DeFi activity, relevant bank records and previous crypto tax calculations.
For unusual or complicated transactions, it can also be worth recording what the transaction actually represented.
For example, a blockchain record might show that tokens moved from Address A to Address B. However, it may not establish whether Address B was your own wallet, a payment to somebody else or an interaction with a DeFi protocol.
That distinction could be important when determining the tax treatment.
Good crypto records should therefore show not only that a transaction happened but, where necessary, what it actually represented.
Could HMRC Check Your Crypto Tax Calculations?
The importance of getting the calculation right doesn't end when the tax return is submitted.
If HMRC opens an enquiry, it may ask you to support the figures reported. This is particularly relevant with crypto because a single capital gain may result from transactions spanning several years, exchanges and wallets.
HMRC's Cryptoassets Manual sets out its approach to crypto taxation. It's record-keeping guidance makes clear that individuals are responsible for keeping their own crypto transaction records.
HMRC also notes that information such as wallet addresses and bank statements may be needed in an enquiry or review.
How CARF Will Increase HMRC's Visibility of Crypto Transactions
From 1 January 2026, UK reporting cryptoasset service providers are required to collect information about users and their cryptoasset transactions.
The first reports will cover the 2026 calendar year and are due to HMRC between 1 January and 31 May 2027.
CARF information won’t itself calculate your UK tax liability. After all, the tax treatment still depends on the underlying transactions and the relevant UK tax rules.
However, HMRC will increasingly receive information about crypto activity independently of the figures taxpayers report.
As a result, it is increasingly important that the figures on your return can be reconciled with, and supported by, your underlying crypto activity.
Before You Submit Your Crypto Tax Calculations to HMRC
Before using the figures from your crypto tax report on your Self Assessment return, take a moment to consider whether the calculation makes sense when compared with your actual crypto activity.
Are your main exchanges and wallets included, and do your principal balances reconcile? Have you investigated significant missing acquisition costs or unusual transactions?
If you have used staking, DeFi or other more complicated arrangements, also consider whether the tax treatment reflects what actually happened.
You don’t necessarily need every minor software warning to disappear before a report can be reliable. Instead, focus on understanding significant discrepancies and making sure the underlying history is sufficiently complete to support the calculation.
If something significant doesn’t make sense, investigate it before filing rather than assuming the software has dealt with it automatically.
Need Help With Your Crypto Tax Reporting?
We have been advising clients on crypto tax since 2017. Our experience combines specialist tax knowledge, previous HMRC experience and a practical understanding of crypto transactions and tax software. We’ve even invested in crypto ourselves.
If something in your crypto tax report doesn’t look right, or your transaction history is particularly complicated, get in touch and we’ll be happy to discuss it with you.
You can explore our other Crypto tax guides or, if you would like to discuss how we could help your business, complete our Business Questionnaire and a member of our team will be in touch.