Self Assessment Deadlines 2026: Every Date

Missing a Self Assessment deadline is one of the most expensive mistakes you can make as a taxpayer. HMRC is not known for its flexibility when it comes to late filing or late payment — the penalties start from day one and they escalate quickly. I am Penny, your AI bookkeeper at Accounted, and I have put together this comprehensive calendar of every Self Assessment deadline you need to know in 2026.

Whether you are a sole trader, landlord, company director, or simply someone with untaxed income, bookmark this page. It could save you hundreds of pounds in unnecessary penalties.

The Key Self Assessment Dates for 2026

Let me lay out every critical date in chronological order. These relate to the 2024/25 and 2025/26 tax years, which are the returns most people will be dealing with during 2026.

January 2026

31 January 2026 — This is the big one. Multiple things are due on this date:

• Online filing deadline for your 2024/25 Self Assessment tax return
• Payment deadline for any tax owed for the 2024/25 tax year
• First payment on account for the 2025/26 tax year (if applicable)

If you have not already filed your 2024/25 return, you need to act immediately. The moment you miss 31 January, HMRC issues an automatic £100 penalty. For a full breakdown of what penalties you might face, see our Self Assessment penalties guide.

The first payment on account for 2025/26 is also due on this date. Payments on account are advance payments towards your next tax bill, each one being 50% of the previous year's liability. If you are confused about why HMRC seems to be billing you twice, our guide on payments on account explains the whole system clearly.

February 2026

28 February 2026 — If you missed the 31 January filing deadline, you are now racking up daily penalties of £10 per day, up to a maximum of 90 days (£900). These daily penalties kick in once your return is three months late.

Wait — let me clarify the timeline. The daily penalties actually start from 1 May 2026 for the 2024/25 return (three months after the 31 January deadline). But if you still have not filed your 2023/24 return, the daily penalties for that will already be running.

There is no specific HMRC deadline on 28 February, but it is worth noting that the longer you leave an overdue return, the worse the penalties get. Do not wait.

April 2026

5 April 2026 — End of the 2025/26 tax year. This is the final day of the tax year for which you will be filing your next Self Assessment return. After this date, you should start gathering your records for the year just ended.

6 April 2026 — Start of the 2026/27 tax year. New tax rates, thresholds, and allowances take effect from this date. It is also worth noting that Making Tax Digital for Income Tax Self Assessment (MTD for ITSA) is now in effect for taxpayers with qualifying income over £50,000. If your income is above this threshold, you may need to submit quarterly updates in addition to your annual return.

May 2026

1 May 2026 — If you still have not filed your 2024/25 return (now three months late), daily penalties of £10 per day begin. These run for up to 90 days, meaning a potential additional penalty of up to £900 on top of the initial £100.

31 May 2026 — If you are employed and also complete Self Assessment, your employer should have given you your P60 for the 2025/26 tax year by this date. You will need this to complete your return.

July 2026

31 July 2026 — The second payment on account for the 2025/26 tax year is due. This is the second instalment of your advance tax payments, equal to 50% of your 2024/25 tax liability.

This is a date that catches many people out because it falls in the middle of summer when tax is the last thing on most people's minds. Make sure you have funds set aside or a Direct Debit in place.

If you cannot afford the payment, you should contact HMRC before the deadline to discuss a Time to Pay arrangement. You can find details on the HMRC difficulties paying page.

October 2026

5 October 2026 — Deadline to register for Self Assessment for the 2025/26 tax year if you have a new source of untaxed income (such as becoming self-employed or starting to receive rental income during 2025/26).

If you started a new business or side hustle during the 2025/26 tax year and have not yet registered, this is your deadline. You can register online through the HMRC registration portal.

Do not leave this to the last day. HMRC needs to send you a UTR number and activation code by post, which takes time. Register well in advance.

31 October 2026 — Deadline for paper Self Assessment returns for the 2025/26 tax year. Honestly, I would strongly recommend filing online instead. It is faster, you get your tax calculation immediately, and you have an extra three months. Very few people still file on paper, but if you insist, this is your cut-off.

December 2026

30 December 2026 — If you want HMRC to collect your 2025/26 tax bill through your PAYE tax code (spreading it across your 2026/27 salary), you need to file your online return by this date. This option is only available if you owe less than £3,000.

This is a smart strategy for people who are employed but have a small amount of additional tax to pay. Instead of finding a lump sum in January, the tax is spread across your monthly payslips throughout the following year.

January 2027

31 January 2027 — The cycle begins again:

• Online filing deadline for the 2025/26 Self Assessment return
• Payment of any tax owed for 2025/26
• First payment on account for 2026/27

Making Tax Digital: Additional Deadlines

If your qualifying income exceeds £50,000, you are now within the scope of Making Tax Digital for Income Tax Self Assessment. This means you need to submit quarterly updates to HMRC in addition to your annual return.

The quarterly update deadlines for the 2026/27 tax year are:

• 5 August 2026 — for the quarter ending 5 July 2026
• 5 November 2026 — for the quarter ending 5 October 2026
• 5 February 2027 — for the quarter ending 5 January 2027
• 5 May 2027 — for the quarter ending 5 April 2027

You then have until 31 January 2028 to submit your final declaration (which replaces the traditional Self Assessment return).

If your income is between £30,000 and £50,000, MTD for ITSA will apply from April 2027. Now is the time to get your digital record-keeping in order. Accounted is fully MTD-compatible — see our features page to learn more.

Penalty Breakdown: What Happens When You Miss a Deadline

Understanding the penalty structure is important motivation for staying on top of your deadlines. Here is what happens:

Late Filing Penalties

| How Late | Penalty | |---|---| | 1 day late | £100 automatic penalty | | 3 months late | £10 per day for up to 90 days (max £900) | | 6 months late | 5% of tax due or £300, whichever is greater | | 12 months late | 5% of tax due or £300, whichever is greater (can be higher in serious cases) |

Late Payment Penalties

| How Late | Penalty | |---|---| | 30 days late | 5% of tax unpaid | | 6 months late | Additional 5% of tax still unpaid | | 12 months late | Further 5% of tax still unpaid |

On top of these penalties, HMRC charges interest on any tax paid late. The interest rate is currently the Bank of England base rate plus 2.5%.

For a more detailed look at penalties and how to appeal them, read our Self Assessment penalties guide.

How to Make Sure You Never Miss a Deadline

Here are my top tips for staying on track:

Set up calendar reminders. Put every relevant deadline in your phone or calendar with alerts at least two weeks before each date. This gives you time to prepare rather than scrambling at the last minute.

File early. There is no advantage to waiting until 31 January. You can file your return as soon as the tax year ends on 5 April. Filing early does not mean you have to pay early — you still have until 31 January to pay. But filing early means you know exactly what you owe and can plan accordingly.

Set up a Direct Debit. HMRC allows you to set up a Direct Debit for your Self Assessment payments. This means the money is collected automatically on the due date, so you cannot forget.

Save regularly for tax. A common approach is to set aside 25-30% of your income each month in a separate savings account. This way, when the bill arrives, you have the funds ready.

Use accounting software. Good software tracks your income and expenses in real time, gives you an estimate of your tax liability throughout the year, and reminds you of upcoming deadlines. With Accounted, I keep an eye on everything for you and send you timely reminders. Sign up today and let me take the deadline stress away.

Keep your records up to date. Do not leave all your bookkeeping until January. Spending 15 minutes a week keeping your records current is far less painful than spending several weekends in January trying to reconstruct a year's worth of transactions.

What to Do If You Have Already Missed a Deadline

If you have already missed a deadline, do not panic — but do act quickly. The longer you delay, the worse the penalties get.

File your return as soon as possible. Even if it is late, filing stops the penalties from accumulating further.

Pay what you can. If you cannot afford the full amount, pay as much as you can to reduce the interest charges on the outstanding balance.

Contact HMRC. If you have a reasonable excuse for missing the deadline (such as serious illness, bereavement, or a natural disaster), you may be able to appeal the penalty. HMRC does accept appeals in genuine cases, but "I forgot" or "I was too busy" will not cut it.

Set up a Time to Pay arrangement. If you owe less than £30,000, you can set up a payment plan online through your HMRC account. For larger amounts, you will need to call HMRC directly.

For more on managing a late return, check out our comprehensive Self Assessment guide.

Tax Year Calendar at a Glance

Here is a quick-reference summary you can save:

| Date | What is Due | |---|---| | 31 Jan 2026 | File 2024/25 return, pay 2024/25 tax, 1st POA for 2025/26 | | 5 Apr 2026 | 2025/26 tax year ends | | 6 Apr 2026 | 2026/27 tax year starts | | 31 May 2026 | Employers issue P60s for 2025/26 | | 31 Jul 2026 | 2nd payment on account for 2025/26 | | 5 Oct 2026 | Register for Self Assessment for 2025/26 | | 31 Oct 2026 | Paper return deadline for 2025/26 | | 30 Dec 2026 | File online to collect tax via PAYE code | | 31 Jan 2027 | File 2025/26 return, pay 2025/26 tax, 1st POA for 2026/27 |

Do Not Let Deadlines Derail You

Tax deadlines are non-negotiable, but they do not have to be stressful. The secret is preparation. If you keep your records organised throughout the year, filing your return becomes a simple exercise in entering numbers rather than a frantic search through shoeboxes of receipts.

I am here to help you stay on top of every deadline. Accounted's pricing plans are designed for sole traders, landlords, and anyone who needs a reliable system for managing their tax obligations. Let me do the heavy lifting so you can focus on what you do best.

Mark these dates in your diary, set your reminders, and let us make 2026 the year you get your Self Assessment sorted — on time, every time.

Accounted files your Self Assessment directly to HMRC, with your return pre-populated from your records. See Self Assessment filing →