Self Assessment deadlines 2026/27: every key date and what happens if you miss them

Self Assessment 2026/27 at a glance

The deadline to file your 2025/26 Self Assessment tax return online is 31 January 2027, and any tax you owe is due by the same date. A paper return must reach HMRC by 31 October 2026. If you need to register for Self Assessment for the first time, the deadline was 5 October 2026. The first payment on account for 2026/27 is also due on 31 January 2027, and the second on 31 July 2027.

Get to 31 January 2027 with the return filed and the tax paid, and you are done. Miss it, and HMRC starts charging penalties from the following day.

What does 2026/27 mean? Tax year dates explained

The UK tax year runs from 6 April to 5 April. People use "2026/27" for two different things, which causes confusion:

• The 2025/26 tax year (6 April 2025 to 5 April 2026) is the year you report in the filing window that ends on 31 January 2027. This is the return most people mean when they search for 2026/27 deadlines.
• The 2026/27 tax year (6 April 2026 to 5 April 2027) is the year you are in now. Its return opens on 6 April 2027.

The 2026/27 return follows the same pattern: register by 5 October 2027, paper return by 31 October 2027, online return and payment by 31 January 2028. HMRC has not yet published those dates in its deadline guide, so check GOV.UK when the new tax year ends.

Which tax return deadline applies to you?

The date depends on how you file, how you want to pay and when you registered. All times are 11:59pm.

• Paper return: 31 October 2026. HMRC must receive it by then.
• Online return: 31 January 2027. This is also the payment deadline.
• Online return if you want to pay through your tax code: 30 December 2026. If you miss this, you pay another way.
• Registered after 5 October 2026: HMRC sends a letter or email with a different deadline, 3 months from the date of the letter or email. You must still pay what you owe by 31 January 2027 or you will get a penalty.
• You can send your return any time on or after 6 April 2026. The deadline is the latest date, not the date to aim for.

Missed an earlier year? File and pay now; see late filing penalties, Self Assessment penalties and payments on account. You can also use HMRC's penalty estimator. Source: GOV.UK Self Assessment deadlines.

5 October 2026: register if this is your first SA year

If you have never filed Self Assessment before, you must register with HMRC by 5 October 2026 if you became liable to file in the 2025/26 tax year. Common triggers:

• You started self-employment
• You started receiving rental income from a property
• You became a company director (in some cases)
• You started receiving foreign or investment income above the allowances
• You had capital gains above the annual exempt amount

Registration is done online at gov.uk/register-for-self-assessment. If you register online, your Unique Taxpayer Reference (UTR) appears in your personal tax account within 72 hours. If you register by post, it usually arrives within 15 working days (21 if you live abroad). You need the UTR to file, so register early.

If you register after 5 October and do not pay all of your tax by 31 January, you may get a 'failure to notify' penalty, based on the amount still left to pay. It is separate from late filing penalties

31 October 2026: paper return deadline

If you choose to file on paper rather than online, the return must reach HMRC by midnight on 31 October 2026. Posting on the 30th is risky; allow extra days for delivery. The form is SA100, plus supplementary pages depending on your income sources (SA105 for property, SA103 for self-employment, and so on).

Most people now file online. Online filing gives you three extra months (to 31 January), a tax calculation as you go and an instant submission receipt. Some filers cannot use the online service, such as trustees of a registered pension scheme and non-resident companies, who send a paper return by 31 January 2027. For everyone else, file online

31 January 2027: the big one

By midnight on 31 January 2027, three things must be done:

1. Submit your 2025/26 online tax return. Through the HMRC online service or commercial software. You get a submission receipt immediately.
2. Pay the balancing payment for 2025/26. That is the difference between your total 2025/26 tax bill and any payments on account you already made in January and July 2026.
3. Pay the first payment on account for 2026/27. If you are in the payments-on-account system, this instalment is due alongside the balancing payment.

The combined bill on 31 January is often larger than people expect, particularly for newly self-employed taxpayers who do not realise the payment on account is on top of the balancing payment. We strongly recommend running the numbers in October or November so there are no surprises in the January cash flow.

31 July 2027: second payment on account

The second instalment of your 2026/27 tax (calculated from the 2025/26 liability) is due by midnight on 31 July 2027. Same payment methods as January: bank transfer, direct debit, debit card, or through your bank.

If your income has dropped this year and you expect the final 2026/27 bill to be lower than 2025/26, you can ask HMRC to reduce the payments on account. This is done either through your online account or by filing form SA303. Be careful, if you reduce them too far and the final bill is higher, HMRC charges interest from the original due dates.

First payment on account for 2026/27: worked example

Each payment on account is usually half of your previous year's tax bill. You need to make them unless your last bill was under £1,000, or you paid more than 80% of it outside Self Assessment, for example through your tax code. Here is how the January 2027 bill adds up.

If this is your first Self Assessment year, there are no earlier payments on account. You would pay the full £5,000 plus the £2,500 first payment on account on 31 January 2027, a total of £7,500. After the 2026/27 return, any difference between £5,000 and your final 2026/27 bill is settled by a balancing payment on 31 January 2028. Source: GOV.UK payments on account.

Capital Gains Tax reporting deadlines for 2026

Capital gains have their own reporting dates. HMRC's CGT reporting deadlines depend on what you sold:

• UK residential property: report and pay any Capital Gains Tax within 60 days of completion using a Capital Gains Tax on UK property account. You also include the sale on your Self Assessment return.
• Other assets, such as shares or a business asset: report the gain on your Self Assessment return by 31 January 2027 for 2025/26. Or report it through the real time Capital Gains Tax service by 31 December 2026 and pay by 31 January 2027.

For the 2026/27 tax year the annual exempt amount is £3,000, and the rates are 18% and 24%. Source: GOV.UK report and pay Capital Gains Tax.

Making Tax Digital dates for 2026/27

Making Tax Digital for Income Tax did not replace the Self Assessment deadline for 2025/26. If you are in scope for 2026/27 (qualifying income over £50,000 in 2024/25), you also send four quarterly updates. HMRC will not apply penalty points for late quarterly updates during 2026/27, but you must send them before you submit your return.

Read our Making Tax Digital for Income Tax guide for who is in scope. Source: GOV.UK quarterly updates.

Penalties if you miss the 31 January deadline

Two penalty regimes run in parallel and you can attract one without the other: late filing and late payment.

Late filing penalties

• 1 day late: automatic £100 penalty, even if you owe no tax
• 3 months late: £10 per day, capped at 90 days (£900 maximum)
• 6 months late: 5% of the tax owed, with a minimum of £300
• 12 months late: a further 5% of the tax owed, minimum £300

So a return filed 12 months late with £5,000 of tax owed attracts £100 + £900 + £300 + £300 = £1,600 in fixed penalties before interest on the unpaid tax.

Late payment penalties

• From 1 February: daily interest on the unpaid tax
• 30 days late: 5% of the unpaid tax
• 6 months late: another 5% surcharge
• 12 months late: a further 5% surcharge

The full breakdown, and how to appeal a penalty if you have a genuine reasonable excuse, is in our late filing penalties guide and late filing vs late payment explainer.

What counts as a 'reasonable excuse'?

HMRC accepts a narrow set of reasons for filing or paying late without penalty. Most of the successful appeals fall into these categories:

• Serious or life-threatening illness around the deadline
• Death of a close relative or partner shortly before the deadline
• An unexpected stay in hospital that prevented filing
• An HMRC system failure (rare, but it happens)
• A fire, flood, or theft that destroyed your records
• Postal delays you could not have predicted (paper filers)

The following are not accepted as reasonable excuses: forgetting, finding the system too difficult, your accountant being late, being too busy at work, or relying on someone else to file for you.

How to pay your Self Assessment bill

HMRC accepts payment by:

• Online or telephone bank transfer (Faster Payments): usually credits the same day if sent before mid-afternoon. The fastest reliable method.
• Direct Debit: set up through your HMRC online account. First-time Direct Debits take up to 5 working days; later payments are quicker.
• Debit card online: usually credits same day. HMRC no longer accepts personal credit cards.
• Through your bank or building society: using a paying-in slip from HMRC. Can take 3 working days.
• By cheque through the post: not recommended for anything close to the deadline. Allow at least 3 working days.

Always include your UTR plus K as the payment reference (for example 1234567890K) so HMRC matches the payment to your account.

What to do now, working back from 31 January 2027

Leaving it to the last week gives you no time to fix a missing record or arrange funds.