HMRC Self Assessment crypto deadline 2026-27: dates and penalties

For the 2025-26 UK tax year, your crypto Self Assessment return and any tax payment are both due by midnight on 31 January 2027. Miss it by a day and HMRC issues an automatic £100 penalty whether you owe £0 or £40,000. This guide covers every deadline, every penalty and what to actually file.

When is the UK crypto tax deadline?

The deadline is fixed and unforgiving. HMRC processed roughly twelve million Self Assessment returns for the 2023-24 tax year and around a million were filed late, generating north of a hundred million pounds in fixed penalties. Crypto holders are over-represented in the late-filer pool because exchange data does not arrive in easy-to-import formats and because tax obligations on swaps surprise people who never converted to fiat. None of that excuses a missed deadline.

The UK tax year for crypto

The UK tax year runs from 6 April to 5 April the following year — a legacy of the calendar reform of 1752. Crypto follows the same dates. A disposal on 5 April 2026 falls in the 2025-26 tax year; the same disposal on 6 April 2026 falls in 2026-27, with a filing deadline a full year later.

Filing and payment deadlines

Three dates matter. Two are firm; one is mostly ignored.

• 31 October 2026 — paper Self Assessment. Almost no crypto filer uses this any more. The form is shorter, but the deadline is three months earlier and penalties for late paper filing apply even if you switch to online afterwards.
• 31 January 2027 — online Self Assessment. The deadline that matters for the 2025-26 tax year. Submit through your HMRC personal tax account. The form is open from 6 April 2026 — early filing means earlier refund if you are owed one and earlier visibility on what you owe if you are not.
• 31 January 2027 — payment of tax owed. The same date. HMRC accepts Faster Payments, Bacs, debit card, and direct debit; credit card payments were withdrawn in 2018. Allow three working days for Bacs to clear or you will trigger late-payment interest.

For an end-to-end walk-through of how to populate the form, see our UK crypto tax calculator guide — the figures it produces drop straight into SA108.

Payments on account

If your prior-year Self Assessment bill exceeded £1,000 and less than 80% of your tax was already collected at source, you owe payments on account toward the next year. Each payment is half of the previous year's bill.

• First payment on account — due 31 January, alongside the balancing payment for the year just ended.
• Second payment on account — due 31 July.
• Balancing payment — the difference between your actual bill and the two payments on account, due the following 31 January.

Capital Gains Tax is excluded from payments on account, but income tax on staking, mining and crypto-funded employment is included. So if £8,000 of staking rewards pushed you into Self Assessment last year, you will be making payments on account for next year too. Reduce them formally via your tax account if your income has dropped — otherwise you are lending HMRC money interest-free.

A small but important rule: if you have a refund coming, payments on account already collected are repaid via your nominated bank account within ten working days of filing. File early and you get the cash back early; the money costs you nothing to recover from HMRC but it does take you submitting the return.

Penalties and interest

HMRC penalties for late Self Assessment are mechanical and stack quickly. The schedule below applies to a return for 2025-26 due 31 January 2027.

Late payment attracts a separate 5% surcharge if not paid 30 days after the due date, another 5% at six months, and another 5% at twelve months. Daily interest on the unpaid balance ran at 7.5% during most of the 2025-26 tax year (Bank of England base rate plus 2.5 percentage points) and adjusts whenever the base rate moves.

What you actually file: SA100 + SA108

Crypto is reported across two HMRC forms:

• SA100 — main Self Assessment return.Covers employment, self-employment, pensions, interest and dividends. Crypto income from staking, mining or paid-in-crypto employment goes on the relevant page (usually "Other UK income" box 17 on SA100, or the self-employment pages SA103 if you mine commercially).
• SA108 — Capital Gains Summary.The page where every crypto disposal lands. You report number of disposals, total proceeds, total allowable costs, gains in the year, losses in the year, and any losses brought forward. Attach a computation working — either a PDF or the "additional information" box — showing how each gain was calculated.

SA108 also needs you to tick the "Other property, assets and gains" box and write in the cryptoasset name. HMRC published a worked example specifically for crypto in 2024 — most tax software produces an attachment that mirrors it line for line.

Where the bill is large, HMRC may also seek security for tax (called a security deposit) but this is rare for individuals and almost never applies to one-off CGT events. For the vast majority of crypto filers, the relevant numbers are the immediate £100 fixed penalty, the 5% surcharges and the daily interest rate.

First-time filers and registration

If 2025-26 is your first year in Self Assessment, you must register with HMRC before you can file. The deadline is 5 October 2026 — six months after the tax year ends. Register at gov.uk and HMRC posts a Unique Taxpayer Reference (UTR) and an activation code within ten working days. Allow three weeks of buffer.

Late registration does not carry its own penalty unless you also file late, but the activation code physically arrives by post. Leaving registration until January 2027 risks missing the filing deadline entirely. Register the moment you know you have a disposal to declare.

What if I miss the deadline?

File anyway. The penalties above keep stacking until you submit, so every additional day of inaction costs more. The order of operations:

1. File the return online through your HMRC account, even if you cannot pay yet.
2. Pay what you can. HMRC's "Time to Pay" arrangement lets you spread liabilities up to £30,000 over twelve months without a formal application — apply via the personal tax account.
3. If you have multiple unfiled prior years of crypto activity, use the HMRC Cryptoasset Disclosure Facility launched in 2024. Voluntary disclosures attract reduced penalties (typically 0 to 30% of unpaid tax instead of 30 to 100%) and protect against criminal investigation in routine cases.
4. Appeal a £100 fixed penalty if you have a "reasonable excuse" — bereavement, serious illness, HMRC system failure. "I forgot" is not a reasonable excuse.

Crucially, filing late is always cheaper than not filing. The £100 fixed penalty hits whether you owe £0 or £40,000. After three months the £10-per-day penalty kicks in regardless of whether the return shows tax owed or a loss. HMRC has confirmed they will not refund the £100 even if the eventual return shows nil tax. Submit something — even a rough estimate that you later amend — to stop the meter running.

HMRC nudge letters and CARF

Since 2024 HMRC has used data from UK and overseas exchanges to send "nudge" letters to suspected crypto holders who have not declared. From 1 January 2026, the OECD's Crypto-Asset Reporting Framework (CARF) obliges reporting CASPs to share transaction data automatically with HMRC, following the same model as bank-account information under the CRS.

Nudge letters are not a formal enquiry. They are an invitation to check your records and amend or file. Ignoring one historically increases the chance of a formal Code of Practice 9 enquiry — which carries far higher penalties. If you receive one:

• Reconcile every wallet and exchange you have used in the last six years.
• Decide whether to amend the year cited or file a fresh voluntary disclosure for any other open years.
• Engage an accountant if your activity included DeFi, NFTs or cross-jurisdiction trading.

Record-keeping HMRC expects

HMRC expects taxpayers to keep all crypto records for at least five years after the 31 January filing deadline of the year of the transaction. For a 2025-26 disposal, that means records held until at least 31 January 2032. If HMRC suspects deliberate or negligent behaviour, the discovery period extends to twenty years.

The minimum dataset for each transaction is:

• Date and time, in UK time.
• Type of transaction (buy, sell, swap, gift, income, spend).
• Asset name and number of units.
• Pound-sterling value at the time, and the rate source.
• Counter-party where applicable (exchange, wallet address).
• Fees paid, separated into trading fees and on-chain gas.
• The wallet or account from which the transaction originated.

Pull CSVs from every exchange at year-end before they delist or shut down. Several UK-active exchanges have closed or restricted UK customer access since 2023; once an account closes, recovering historical data can be slow or impossible. Tools such as Koinly archive the data as soon as it syncs, which is one of the underrated benefits of an annual subscription.

How to actually pay HMRC

HMRC accepts the following methods for Self Assessment payments:

• Faster Payments— same-day or next-working-day, using HMRC's sort code 08 32 10 and the Cumbernauld or Shipley account number printed on your statement. Quote your UTR followed by "K" as the reference.
• Bacs transfer — three working days; only suitable if you start at least four days before the deadline.
• Direct debit — set up the first time can take five working days; subsequent payments same-day.
• Debit card via gov.uk — fastest but may incur a fee on corporate cards. Personal debit cards are free.
• At a bank or Post Office — only with a posted HMRC payslip. Cheques by post must arrive by the deadline.

Credit cards have not been accepted since January 2018. Cryptocurrency is not accepted as payment for HMRC liabilities under any circumstance. For a deeper look at deductions, see claiming crypto losses with HMRC. The full Self Assessment guidance lives on the gov.uk Self Assessment hub.