How to make a voluntary disclosure of crypto to HMRC, step by step

Let's start where you actually are. You're not trying to decide whetherto come forward; you've made that call, and it's the right one. What you need now is the map: exactly what to click, what to gather, how the timings work, and roughly what the bill will look like. The good news is that HMRC runs a purpose-built route for people in precisely your position, and coming forward yourself (before HMRC contacts you) keeps the cost far lower than being caught. This guide walks the whole thing, calmly, one stage at a time.

The route is the Cryptoassets Disclosure Service, which sits inside HMRC's wider Digital Disclosure Service. It's online, it's designed for individuals with undeclared crypto income or gains, and it lets you settle the tax, interest and a (usually much smaller) penalty in one go. If you want the full picture of the penalty bands and time limits first, read what happens if you don't declare crypto to HMRC alongside this; that guide explains the numbers, and this one explains the mechanics.

Before you start: why doing this now matters

One fact shapes everything below. Making your disclosure before HMRC contacts you counts as an unprompted disclosure, which unlocks the gentlest penalty band. If you wait until a nudge letter or an enquiry lands first, your status flips to promptedand the minimum penalty jumps. For a careless mistake (the honest classification for most people who simply didn't realise a swap or sale was taxable), the floorfor an unprompted, full disclosure is nil; for a prompted one it starts at a minimum of 15%. Note the word floor: nil is the best you can reach, not a default you get automatically. Where you actually land within the band depends on how fully you help HMRC, which is covered just below. That's the whole reason timing matters, and it's the single most valuable thing you control.

Nil is earned, not given. HMRC reduces the penalty within the band according to the quality of your disclosure: how completely you tell them what happened, how much you help them understand it, and whether you give access to your records. Do all three fully and a careless-unprompted penalty can reach nil or near-nil; do them partially and you'll sit higher up the band. A vague or half-complete disclosure of careless behaviour can still carry a penalty of up to 30%. The exact sub-bands are set out in the guide on what happens if you don't declare.

You don't need every figure worked out to protect your status. Your unprompted status is set the moment you notifyHMRC that you intend to disclose (step 1 below), as long as HMRC hasn't already been in touch about it. So the notification is the thing to do first, even before the arithmetic. One important distinction: keeping unprompted status for penalty purposes allows for full detail to follow within a reasonable time, but that is a separate thing from the submission deadline. Once HMRC acknowledges your notification, you get a hard 90-day window to submit the complete disclosure. A submission after day 90 is rejected on the procedure, whatever your penalty status. So: notify first to protect your terms, then submit the full detail inside 90 days without exception.

If a letter has alreadyarrived, don't worry, you still disclose the same way, but the penalty bands shift upward because you are now treated as prompted. For careless behaviour, the prompted minimum is 15% rather than the 0% floor available to an unprompted disclosure. That gap is exactly why early notification is protective, and it's why, if a letter has landed, you should start with what a nudge letter means and what to do first.

The disclosure, step by step

The Cryptoassets Disclosure Service runs as a clear five-stage process. Here it is in order, with the timings that apply at each point.

1. Notify HMRC (this is the step that protects your terms). Using the online form on GOV.UK, tell HMRC you intend to disclose unpaid tax on cryptoassets. You do notgive any figures yet, only that you're coming forward. HMRC then issues you a Disclosure Reference Number and a payment reference number, typically within 15 working days. Making this notification before any HMRC contact is what establishes you as unprompted.
2. Use your 90-day window to work out the real number. From the date HMRC acknowledges your notification, you get 90 days to gather your records, calculate the undeclared gains and income for each year, and work out the interest and penalty. This 90 days is a hard procedural deadline: a disclosure submitted after day 90 is rejected on the process, so treat it as fixed. If your history is genuinely complex, you can ask HMRC in writing, beforethe deadline runs out, for more time. This is the stage that takes the most effort, and it's covered in detail below.
3. Submit the full disclosure online.Within the 90 days, submit the complete detail: every undeclared gain and income figure by year, the Capital Gains Tax and any Income Tax owed, the interest, and the penalty you're offering (as a percentage of the tax, based on your behaviour). Quote your payment reference number. Full, honest transparency here is exactly what earns the biggest penalty reduction; a vague or partial disclosure works against you and can slow everything down.
4. Pay within 30 days of submitting. You pay the full amount (tax, interest and penalty) within 30 days of submitting your disclosure, using your payment reference. If you can't pay it all at once, you must arrange a Time to Pay plan with HMRC before you submit, not after (more on that below). HMRC then writes to confirm it has received your payment.
5. HMRC reviews and settles. HMRC checks your submission for completeness and accuracy, then either accepts your offer (the usual outcome when a disclosure is full, honest and accurate), creating a binding settlement, or comes back for more information. A settlement letter typically follows within a few weeks of payment. If HMRC finds the disclosure knowingly false or incomplete, it can reject it, which is exactly why getting the detail right the first time matters.

Which years, and what to calculate

A common worry is “how far back do I have to go?” The number of years depends on how HMRC classifies the behaviour, which it decides after your disclosure, not something you label yourself. In outline: reasonable-care mistakes reach back 4 years, careless behaviour 6 years, and deliberate behaviour up to 20 years. The full explanation of those windows lives in the guide on what happens if you don't declare, so it isn't repeated here. The practical point: the years in scope are counted from when the undeclared transactions actually happened, so before you decide your scope, pin down the dates of your earliest disposals. Exactly which years apply comes down to your particular facts.

For each year in scope, you need to produce, in pounds:

• A transaction list: date, type (buy, sell, swap, gift, staking, lending), the amount acquired or disposed of, and the cost or proceeds in GBP at the time.
• Cost basis under HMRC's matching rules: the same-day rule first, then the 30-day rule, then the Section 104 poolfor everything else, using the pool's average cost. NFTs aren't pooled; each is tracked on its own. Getting this order wrong is one of the most common ways a spreadsheet inflates the gain.
• The gain or loss per disposal, then netted per year. Losses in one year can be offset against gains, and unused losses carry forward, so include your loss years too; leaving them out means you overpay.
• Capital Gains Tax owed per year:net gains minus that year's annual exempt amount (it was £3,000 for 2024/25, higher in earlier years), taxed at the applicable rate.
• Income Tax, if relevant: staking rewards, lending yield and most airdrops are income, not capital gains, valued in pounds on receipt and taxed at your marginal rate. Mixing these up is a frequent error.
• Interest,calculated daily from each year's due date (31 January after the tax year) to your payment date. HMRC will reject a disclosure where the interest is wrong or guessed, so this has to be exact, not a rough add-on. Interest isn't negotiable.

If you can't find records for some old wallets or coins, don't invent numbers. State clearly what you can and can't evidence. HMRC far prefers an honest partial disclosure to fabricated figures, and there are sensible ways to handle genuinely lost records. Whatever you do, aim to disclose everything you can find; the goal is a full and correct picture, never the smallest number you think you can get away with.

Roughly what it will cost

Three things make up the bill: the tax you should have paid, the interest on it, and a penalty. The tax and interest are owed whatever you do; only the penalty moves with your behaviour and your timing. For a careless omission disclosed unprompted, the penalty flooris nil, but you only reach it by telling HMRC the full story, helping them understand it, and giving them access to your records. Fall short on any of those and you sit higher in the band (up to 30% for careless behaviour). So treat nil as the best case you earn, not the default. The exact bands, and how “quality of disclosure” reduces the penalty within them, are set out in full in the guide on what happens if you don't declare rather than repeated here.

One more honest point worth knowing: HMRC decides your behaviour band from the facts, not from the box you tick, so be straightforward about what happened. (The three-year timing restriction is covered in the callout near the top, since it's really a reason to notify sooner.) Your final band and figure are HMRC's judgment, based on the facts you present.

If you can't pay it all at once

This is a common and completely normal situation, and it has a defined answer: Time to Pay. The one rule to remember is that you must agree it before you submit your disclosure, not after. A Time to Pay plan spreads the payment over months (often up to around a year, sometimes longer for very large sums). It does not reduce what you owe; it only changes the schedule, and interest keeps accruing on the outstanding balance while you pay it down.

To set one up, call HMRC's cryptoassets helpline on 03000 55 22 94 (Monday to Thursday 9am to 5pm, Friday 9am to 4:30pm) before you submit, explain what you can afford, and agree the terms. Then reference the arrangement in your disclosure. HMRC will expect you to keep to the plan; missing payments can undo the settlement and trigger normal debt recovery, so only agree to instalments you can genuinely meet.

The parts that are genuinely case-specific

Most crypto disclosures are more straightforward than people fear. But a few situations are genuinely fact-dependent, and the honest answer is “it depends, so describe exactly what happened and let HMRC agree the treatment.” These come up often enough to flag:

• Behaviour band.Careless, deliberate, or reasonable care is HMRC's call, based on your records and circumstances, not a label you choose.
• Transfers between your own wallets.Moving crypto between wallets you own isn't a disposal. If you moved coins from Exchange A to a hardware wallet and on to Exchange B, each step is a transfer and none of it is taxable. But if you sold on A, moved the proceeds to a personal wallet, then boughtagain on B, that's two separate taxable events (a sale and a purchase), not a single transfer. The distinction matters, so be precise about what you actually did with each movement.
• DeFi, staking pools, forks, wrapped tokens and bridges.The treatment of liquidity-pool tokens, staking derivatives, forks, wrapping and cross-chain bridging isn't fully settled in HMRC guidance, and it's still evolving. This is a known grey area rather than something you've got wrong. If your activity includes it, set out the transaction in detail and state the treatment you've assumed in your disclosure narrative, so HMRC can agree or adjust it rather than treat it as hidden.
• Theft, scams and rug-pulls. Whether a loss can be claimed depends heavily on the evidence; our guide on stolen or scammed crypto explains the negligible-value route.

None of these should stop you disclosing. They're simply the points where a clear written explanation, and often a qualified adviser, earns its keep.

What to do now

Here's the calm version of the whole thing:

1. Notify HMRC first via the Cryptoassets Disclosure Service to lock in your unprompted status while it's still yours to claim.
2. Work out the real number for every year in scope, HMRC's way, using the Section 104 pool and the same-day and 30-day rules, including your loss years and any income from staking or airdrops. Disclose everything you can evidence, in full.
3. Disclose in full and keep your workings, then pay within 30 days, or meet the Time to Pay plan you arranged first.

Not even sure how much of your activity is taxable? Start with how UK crypto tax works, and remember that from 2026 UK exchanges report to HMRC under CARF, which is why coming forward now matters. This is general information, not personal tax advice. If the amounts are material, several years are involved, or your history is large or messy, it's well worth speaking to a qualified adviser before you disclose; a good one can also help argue the gentler behaviour band on your behalf.

Sources

• GOV.UK: Tell HMRC about unpaid tax on cryptoassets (the Cryptoassets Disclosure Service): notification, 30-day payment window, 15 working days for reference numbers, helpline 03000 55 22 94, interest and penalties
• GOV.UK: Your guide to making a disclosure (Digital Disclosure Service): notification, Disclosure Reference Number, 90-day disclosure window, behaviour, penalties, payment and settlement
• HMRC Compliance Handbook CH82420: unprompted versus prompted disclosure, and why unprompted unlocks the lower penalty band
• HMRC Compliance Handbook CH82430: quality of disclosure (telling, helping, giving access) and how it reduces the penalty within the band
• HMRC Compliance Handbook CH82470: maximum and minimum penalties by behaviour, prompted and unprompted
• HMRC Compliance Handbook CH82465: timing of disclosure, and the restriction where more than three years have passed
• HMRC Cryptoassets Manual CRYPTO22200: Section 104 pooling, the same-day and 30-day rules, and the separate treatment of NFTs
• HMRC Debt Management and Banking DMBM800040: Time to Pay principles (it changes the schedule, not the amount owed)
• GOV.UK: Pay tax on cryptoassets (general HMRC crypto tax treatment and record-keeping context)
• HMRC: Cryptoassets Manual