How To Report Crypto On A UK Tax Return: SA108 Box By Box

Crypto does not get its own tax return in the UK. It goes on the ordinary Self Assessment return: gains on the SA108 capital gains summary, which has carried a dedicated cryptoassets section since the 2024 to 2025 return, and income from staking, mining or airdrops on the main SA100. This guide walks the whole filing, box by box.

Most of the confusion is not about tax law. It is about mechanics. People know a disposal is taxable, and they still do not know which page the number goes on, whether an exchange CSV counts as the computation HMRC asks for, or what to do when the same tokens produced both income and a gain. Those are the questions this guide answers. For the treatment behind the figures, our guide to UK crypto tax and the HMRC rules covers the ground first.

Do You Have To Report Crypto To HMRC At All?

Holding crypto is not a reportable event. What creates the filing duty is a disposal that produces a taxable gain, or a receipt that counts as income. HMRC sets out both tests in its own guidance, and neither is a judgement call.

When a crypto gain has to go on a tax return

HMRC treats four things as disposals of cryptoasset tokens: selling them, exchanging them for a different type of cryptoasset, using them to pay for goods or services, and giving them to another person other than your spouse, civil partner or a charity. A crypto to crypto swap is a disposal, which is the point most people miss. If your total gains for the tax year exceed the annual exempt amount, you must report the gain and pay Capital Gains Tax.

The annual exempt amount is £3,000 for individuals, and gov.uk records the same £3,000 figure for the 2025 to 2026 and 2026 to 2027 tax years on its rates and allowances table. Separately, you must send a tax return if you had to pay Capital Gains Tax when you sold or disposed of something that increased in value.

When crypto income has to go on a tax return

Tokens you receive from mining, staking, lending or liquidity pool arrangements count as income, and HMRC says this explicitly includes income earned from decentralised finance. Where you are not carrying on a trade, HMRC treats those tokens as other taxable income.

There is a threshold here that a lot of readers can use. You get up to £1,000 of allowance each tax year for trading and miscellaneous income. HMRC asks you to contact it if your total miscellaneous income from all sources is between £1,000 and £2,500, and to register for Self Assessment if it is over £2,500.

What if you only bought and held?

Buying tokens and holding them creates nothing to report. HMRC is direct about this: if you purchased the tokens yourself, you do not pay tax when you buy them. The duty starts at disposal. A wallet that only ever received deposits and never sent, swapped or spent anything generates no entry on a return.

What if you made a loss?

A loss is worth reporting even though it does not create tax. HMRC says you can use capital losses on other assets to reduce your gain, but you will need to report them to HMRC first. An unreported loss is not available to set against a later gain, so a bad year is exactly the year to file.

What if your gains are under the allowance but proceeds are large?

Work the gain, not the turnover. The test HMRC states on its cryptoassets page is whether your total gain for the tax year is above the tax-free allowance. Someone who moved six figures through an exchange and netted a £900 gain is below the threshold on that test. Note that other reporting rules can still pull you into Self Assessment for unrelated reasons, so check the whole picture rather than the crypto alone.

Registering For Self Assessment And Getting A UTR

You cannot file until HMRC knows you intend to. Registration produces a Unique Taxpayer Reference, the ten digit number every later step needs, and it has its own deadline that sits three months before the filing deadline.

The 5 October deadline

You must tell HMRC by 5 October if you need to complete a tax return for the previous year and you have either not sent a tax return before, or registered before but did not need to send one for the 2024 to 2025 tax year. The previous tax year started on 6 April 2025 and ended on 5 April 2026, so the registration deadline for that year is 5 October 2026.

What happens if you register late

Registering late does not remove the duty, it changes the clock and adds a penalty risk. On the timing, HMRC says it will send a letter or email with a different deadline, three months from the date on that letter, and that you must still pay the tax you owe by 11:59pm on 31 January 2027.

The penalty is a separate matter with its own source. HMRC states that if you register after 5 October and do not pay all of your tax bill by 31 January, you may get a failure to notify penalty, based on the amount still left to pay and issued within 12 months after HMRC receives your return.

If you have filed before but not last year

A dormant Self Assessment record is a common trap for crypto investors, who often file in the years they sell and not in the years they do not. HMRC notes that if you registered before but did not send a return last year, you may need to reactivate your Self Assessment account, and the registration service tells you how.

How long the UTR takes

We do not publish a turnaround figure, because HMRC does not commit to one and the wait moves through the year. What matters for planning is the order: the UTR has to exist before the online return can be filed, so registration in the week before the January deadline is a risk you take deliberately, not an administrative afterthought.

Which Pages Crypto Goes On: SA100, SA108 And SA103

The Self Assessment return is a core form plus supplementary pages. Crypto can touch three of them, and which ones depends on whether the money was a gain, income, or trading profit.

The SA100 main return and the question 7 tick box

The SA100 is the core return. On page TR 2 it asks a set of yes or no questions that determine which supplementary pages you get. Question 7 is the Capital Gains Tax summary question: if you sold or disposed of any assets, read the notes to decide whether you have to fill in the capital gains summary page. The form pairs it with a second yes or no box, "Computations provided", which tells HMRC whether your workings are attached.

Crypto income that is not trading goes on the SA100 itself. On page TR 3, box 17 is "Other taxable income, before expenses and tax taken off", box 18 is the total of allowable expenses, box 19 is any tax taken off box 17, and box 21 is where you describe the income in boxes 17 and 20. For staking rewards, "Staking and DeFi rewards" in box 21 is the description that box is asking for.

SA108, the capital gains summary

SA108 is where gains go. Since the 2024 to 2025 return it has had a cryptoassets section of its own, which we walk box by box below. HMRC states the requirement in one sentence at the top of the form: you must enclose your computations, including details of each gain or loss, as well as filling in the boxes.

SA103 if you are trading

Trading is the exception, not the norm. HMRC treats mining, staking and lending receipts as other taxable income where you are not carrying on a trade, which means the trading case has to be established on the badges of trade rather than assumed because the activity was frequent. Where it is established, the profit is self-employment income on the SA103 self-employment pages and it carries National Insurance, not Capital Gains Tax. Getting this the wrong way round changes the rate, the allowances and the return itself, so it is worth settling before you file rather than after.

Which figure goes where

The Cryptoassets Section Of SA108, Box By Box

This is the part of the return that changed. HMRC confirms that where you report a gain on a Self Assessment return you should complete it in pound sterling, in the cryptoassets section, available on returns for the tax year 2024 to 2025 onwards. Before that, crypto disposals were reported in the "other property, assets and gains" section alongside everything else. The boxes below are from the SA108 for the 2025 to 2026 tax year and its published notes.

Box 13.1 Number of disposals

The notes say to put the number of disposals you made for the year in box 13.1, and to ignore disposals you do not make in your own capacity, for example disposals you make as a trustee. Every taxable disposal counts, so each crypto to crypto swap counts, and for an active DeFi wallet this number can run to thousands. That is a count, not a judgement, and it has to reconcile with the computation you attach.

Box 13.2 Disposal proceeds

Put the total disposal proceeds, before taking off any reliefs, claims or elections, in box 13.2. Gross, not net. A common error is entering the net gain here, which makes the section internally inconsistent the moment HMRC reads it against box 13.3.

Box 13.3 Allowable costs, including purchase price

Your total allowable costs go in box 13.3. This is the pooled cost attributable to what you disposed of, not what you originally paid for everything you hold. Working that number out is the actual labour in a crypto return, and it is the reason our UK crypto tax accounting service exists.

Box 13.4 Gains in the year, before losses

Put the total of any gains you made in box 13.4, after any reliefs, claims or elections that give deductions from total gains. The notes add that the figure in box 13.4 must include any gains within the box 13.7 amount, so real time reported gains are not excluded here, they are included and then accounted for separately.

Box 13.5 Losses in the year

Box 13.5 takes the total of any losses made on the disposals, after the effect of any relief, claims or elections. The same inclusion rule applies: this figure must include any losses within the box 13.7 amount. Gains and losses go in separate boxes rather than being netted into one, which is what lets HMRC see the gross activity.

Box 13.6 Claim or election code

If you are making a claim or election, box 13.6 takes the relevant three letter code, and the notes are explicit that you must also tell HMRC in your computation. The code table is in the SA108 notes. The code alone is not the claim; the computation carries it.

Boxes 13.7 and 13.8, real time transaction returns

Box 13.7 is for the overall gain or loss on crypto disposals you already included when you used the real time Capital Gains Tax service, and box 13.8 is the tax on those gains you have already paid. These two boxes are how the annual return absorbs a mid-year report without taxing the same gain twice.

The computation you have to enclose

The instruction at the top of the SA108 is a requirement, not a suggestion: you must enclose your computations, including details of each gain or loss, as well as filling in the boxes. A raw exchange CSV is not a computation. A computation shows, per disposal, the date, the asset, the proceeds, the pooled cost attributed, and the resulting gain or loss, in sterling, tying to the totals in the boxes.

What the section does not change

The new section changed where the numbers sit, not how they are worked out. Pooling, the same day rule and the 30 day rule all apply exactly as before, and the annual exempt amount is unchanged by which section of the form you use.

Reporting Staking, Mining And Airdrop Income

Income and gains are two separate reporting streams on the same return, and the same tokens routinely produce both. Getting the sequence right is what stops the value being taxed twice.

Where the income goes

Where you are not trading, HMRC treats mining, staking and lending receipts as other taxable income, which is box 17 on page TR 3 of the SA100, described in box 21. Gains on those same tokens later go in the cryptoassets section of the SA108. One tax year, two sections, one set of tokens.

Income first, then gains on the same tokens

HMRC sets out the order plainly. If you sell a cryptoasset that you have paid Income Tax on at a later date, you calculate Capital Gains Tax as normal on any increase in value since you received them. The value you already declared as income becomes your cost for the gain calculation. HMRC states the same principle from the other direction: if you have paid Income Tax on any part of your cryptoasset token value, you will not pay Capital Gains Tax on that amount.

The £1,000 trading and miscellaneous income allowance

The allowance is per tax year and covers trading and miscellaneous income from all sources, not crypto alone. HMRC asks you to contact it where the total is between £1,000 and £2,500, and to register for Self Assessment above £2,500. A reader with £600 of staking rewards and £700 of freelance income is over the allowance even though neither source is on its own.

Airdrops

Airdrops turn on whether anything was given in return. HMRC deals with them in the Cryptoassets Manual at CRYPTO22350 on the capital gains side, and the receipt side follows the income tests above. An unsolicited token that arrived for nothing, with nothing done to earn it and no trade being carried on, is not the same event as a reward paid for providing a service, and the two do not go in the same box.

If your employer pays you in tokens

Employment is a different route again. Cryptoassets received as employment income count as money's worth and are subject to Income Tax and National Insurance. HMRC says exchange tokens like bitcoin are readily convertible assets, and that UK employers must pay your Income Tax and National Insurance through PAYE before they pay you. Where your employer has not operated PAYE, HMRC says you will need to pay it yourself through a Self Assessment return in pound sterling.

The Real Time Capital Gains Tax Service

There is a second route to reporting a gain, and most crypto investors do not know it exists. It is not a shortcut around the return, but it can settle a gain earlier than the following January.

When you can use it

For gains other than UK residential property, HMRC says you report in the tax year after you sold or disposed of an asset if you use a Self Assessment tax return, and that if you are eligible you may be able to use the real time Capital Gains Tax service to report by 31 December in the tax year after the sale. The cryptoassets guidance lists the same two options: completing a Self Assessment tax return at the end of the tax year, or using the Capital Gains Tax real time service.

How it interacts with the SA108

The real time service does not replace the annual return where you are filing one. That is exactly what boxes 13.7 and 13.8 are for: the gain reported in real time goes into the box 13.4 total, the overall real time gain or loss is stated in box 13.7, and the tax already paid on it goes in box 13.8. The return then reconciles rather than double counts.

Working Out The Figures Before You Fill In A Box

Every box above takes a number that has to come from somewhere. The calculation rules are where crypto returns actually go wrong, and no amount of care with the form fixes a wrong pool.

Section 104 pooling

HMRC requires you to group each type of token you own into pools and work out the pooled cost for each type. Each time you buy or receive tokens you add what you paid to the pool, and each time you dispose you deduct an equivalent proportion of the pooled costs. HMRC illustrates it with 400 tokens costing £500 in total, an average of £1.25 each, so a sale of 200 carries £250 of cost. Our guide to the section 104 pool and what happens when you move crypto between platforms covers the case that breaks most spreadsheets.

The same day and 30 day rules

Pooling has two exceptions. HMRC says do not pool the cost of tokens you buy on the same day that you sell tokens of the same type, or within 30 days of selling tokens of the same type. In those cases the rules follow the share identification rules in helpsheet HS284. Anyone who rebalances a position inside a month is in this territory whether or not they intended to be.

Allowable costs you can and cannot deduct

HMRC lists the allowable costs as transaction fees, advertising for a buyer or seller, drawing up a contract for the transaction, making a valuation to work out your gain, and a proportion of the pooled costs. It also names two exclusions: costs you have already deducted against profits for Income Tax, and the costs of mining activities such as equipment or electricity.

Everything in pounds sterling

Both HMRC cryptoasset pages say the same thing: the return is completed in pound sterling. That means a sterling value at the date and time of each transaction, including for a crypto to crypto swap where no fiat moved at all. A USD denominated exchange export is a starting point, not an answer.

The rates the figures meet

For the 2025 to 2026 tax year, gov.uk records Capital Gains Tax rates of 18% and 24% for individuals, not including carried interest gains.

Which of the two applies depends on your income rather than on the size of the gain alone. The current rates page sets out the method for gains made from 6 April 2026: work out your taxable income, work out your total taxable gains, deduct the tax-free allowance, add the result to your taxable income, and if that amount is within the basic Income Tax band you pay 18%, with 24% on any amount above it.

Deadlines, Payments On Account And Penalties

HMRC publishes every date on one page, and the Self Assessment deadlines for the tax year that ended on 5 April 2026 are below.

The filing deadlines

HMRC states that it must receive your paper tax return by 11:59pm on 31 October 2026, and that you must submit an online return by 11:59pm on 31 January 2027, in each case or you will get a late filing penalty. You can send either any time on or after 6 April 2026.

Paying through your tax code

There is a quieter deadline worth knowing. HMRC says that if you want to pay your Self Assessment bill through your tax code, you must submit the online return by 11:59pm on 30 December 2026, and that if you miss it you will have to pay another way. Filing a month early can therefore change how you settle the bill, not just when.

Payments on account

HMRC says the tax is due by 31 January and that there is a second payment deadline of 31 July if you make payments towards your bill, known as payments on account. This catches crypto investors who have a large gain in one year, because the payments on account are set against the following year even where the gain does not repeat.

Late filing penalties

HMRC publishes the late filing penalties as a fixed sequence: an initial £100 penalty, then after 3 months daily penalties of £10 per day up to a maximum of £900, then after 6 months a further penalty of 5% of the tax due or £300 whichever is greater, and after 12 months another 5% or £300 charge whichever is greater.

Late payment penalties

Filing and paying are penalised separately. HMRC says you will get penalties of 5% of the tax unpaid at 30 days, 6 months and 12 months, and that you will also be charged interest on the amount owed. A return filed on time with the tax unpaid still attracts these.

Appealing a penalty

HMRC states that you must pay a penalty within 30 days of the date on the penalty notice, and that if you have a reasonable excuse you can appeal against a penalty. Whether a given set of facts is a reasonable excuse is decided on the facts, so the appeal route is worth reading before assuming a penalty is final.

Amending A Return You Have Already Filed

Crypto returns get amended more often than most, because the data arrives late: an exchange closes, a wallet is remembered, a missing acquisition turns up. HMRC has a defined window for fixing it yourself and a different route once that window closes.

The 12 month window

You can correct a tax return within 12 months of the Self Assessment deadline, online or by sending another paper return. HMRC gives the worked example itself: for the 2024 to 2025 tax year, you will usually need to change your return by 31 January 2027. On an online return, HMRC says you must wait 3 days, 72 hours, after filing before updating it.

Amending on paper

For a paper amendment, HMRC says to send the corrected pages to the address on your Self Assessment paperwork, writing amendment on each page and including your name and Unique Taxpayer Reference. Where you cannot find the address, HMRC gives Self Assessment, HM Revenue and Customs, BX9 1AS.

After the 12 month window

Once it is more than 12 months after the Self Assessment deadline, HMRC says you will need to write to HMRC to report income you did not include, or to claim overpayment relief if you think you have overpaid. The letter should give the tax year, why you think you have paid too little, how much you think you have underpaid, and your signature.

Earlier years and the Cryptoasset Disclosure Service

For unpaid tax on cryptoassets from earlier years there is a purpose built route. HMRC says to use its service to tell HMRC about unpaid tax on cryptoassets, covering exchange tokens, NFTs and utility tokens, and warns that if you do not contact it to declare unpaid tax you could be liable to additional interest and penalties. HMRC also draws the line clearly: income or gains from the current or previous tax year go on the Self Assessment return, not the disclosure service. Our guide to voluntarily disclosing unpaid crypto tax to HMRC walks that process.

The Records HMRC Expects You To Keep

Records are not filed with the return, but they are what the return has to survive. HMRC says plainly that it will ask to see them if it carries out a compliance check.

What the records must show

For each pool of tokens, HMRC says you must keep separate records for each transaction including the type of tokens, the date you disposed of them, the number disposed of, the number you have left, the value in pound sterling, bank statements, and the pooled costs before and after the disposal. It adds that you may also want to keep wallet addresses. On the income side the required records are the token type, the date received, the number received, the number you hold in total, the sterling value, bank statements, and the disposal details.

Why an exchange report is not a tax calculation

HMRC makes this point itself, and it is the single most useful sentence on the page for anyone relying on a platform export. Some exchanges provide reports of your transactions, and HMRC says these can be essential for working out how much tax you owe, but that they are not tax calculations and will not keep track of your pooled costs. It concludes: you must keep your own records of your transactions.

How long the reporting picture is changing

The record you keep is no longer the only record HMRC sees. Reporting obligations on UK cryptoasset service providers are widening, which we cover in the UK crypto reporting mandate and in what HMRC can already see about your crypto. The practical consequence is that a return should be built to agree with third party data, not merely to be defensible in isolation.

Where A Crypto Tax Accountant Fits

Nothing above requires an accountant. A reader with one exchange account, a handful of disposals and clean records can complete the cryptoassets section from their own workings. The work becomes specialist at the point where the pooled cost is genuinely hard to establish: transfers between platforms, a closed exchange, DeFi positions, or a history that starts before the records do.

What a crypto tax accountant produces is the computation the SA108 demands. CountDeFi are crypto tax accountants: we reconcile the full transaction history, build the section 104 pools, and hand over the figures and the supporting computation. Who signs and files the return is a separate question, and our guide to who does what on a UK crypto return and who can file it sets out that split. If you want the reconciliation done for you, that is our crypto tax accounting service.

What to have ready

• A complete list of every exchange, wallet and chain you used in the year, including accounts you closed
• Full transaction history from each, not just the year being filed, because the pooled cost carries forward from inception
• Your UTR, or confirmation that registration is in progress
• Any income streams separated from disposals, since they go on different pages of the return
• Prior year returns where crypto was reported, so the opening pools agree with what was filed