Self Assessment Deadlines 2025/26, October to July

The Self Assessment deadlines 2025/26 apply to income earned in the tax year that ended on 5 April 2026. Online returns, and any tax you owe, are due by 31 January 2027, with an earlier 31 October 2026 deadline for paper returns. Anyone making payments on account has a further instalment due on 31 July 2027.

Didn’t register by 5 October? You haven’t lost the chance to file on time. Your filing deadline may move later, depending on when HMRC issues your notice to file, but the tax is still due on 31 January 2027, and that Sunday can bring a first instalment towards next year’s bill on top. Before then, the paper deadline of 31 October 2026 is the next date to land.

This checklist is for anyone sending a 2025/26 return: sole traders, landlords, partners, and employees or pensioners with untaxed income on the side.

Five things change which dates apply to you: registering late, filing on paper, making payments on account, being signed up to Making Tax Digital, and employing staff.

Self Assessment deadlines 2025/26, date by date

Every date below flows from your 2025/26 return, even the ones in 2027. A tax year ends on 5 April, and HMRC then gives you until the following January to report it and pay, which is why one year’s paperwork runs across three calendar years.

Here’s each date in order, with who it applies to and what missing it costs.

5 April 2026: the 2025/26 tax year ended

This date is the cut-off line. Income and expenses up to and including 5 April 2026 go on your 2025/26 return, and anything after it belongs to 2026/27. You’ve been able to send the 2025/26 return since 6 April 2026.

5 October 2026: registration for 2025/26 (now passed)

You had to tell HMRC by Monday 5 October 2026 where you need a 2025/26 return and either you’d never sent one before, or you were registered but didn’t have to send one for 2024/25. Registering is what gets you the Unique Taxpayer Reference (UTR) you file under.

A penalty for registering late is possible rather than automatic. What decides it is covered in the section on late registration further down.

31 October 2026: paper returns for 2025/26

If you’re filing on paper, HMRC has to receive your return by 11:59pm on Saturday 31 October 2026. Posting it on the day isn’t enough, so leave time for the post.

A paper return that arrives late picks up the £100 late filing penalty and the charges that follow it. Online returns run to a later deadline, covered below.

30 December 2026: file online to pay through your tax code

This one’s optional, and it only suits people who already pay tax through PAYE, for example as an employee or through a company pension.

If you owe less than £3,000 for 2025/26 and file online by 11:59pm on Wednesday 30 December 2026, HMRC can collect the bill through your tax code instead of you paying it in one go. (Paper filers get the same option if their return arrived by 31 October.)

A few limits apply. You can’t make a part payment to squeeze the bill under £3,000, and HMRC won’t collect it this way if you’d pay more than half your PAYE income in tax, or more than twice your usual tax. Miss 30 December and you’ll need to pay another way, by 31 January 2027.

31 January 2027: file online and pay

This is the big one, because several deadlines land on the same day. By 11:59pm on Sunday 31 January 2027, you need to:

• File your 2025/26 return online.
• Pay your balancing payment, which is whatever you still owe for 2025/26.
• Make your first payment on account towards 2026/27, if they apply to you.

Because the 31st is a Sunday, the money has to reach HMRC by Friday 29 January 2027. Faster Payments and card payments (debit or corporate credit) are the exceptions to that weekend rule; Bacs, CHAPS, cheque and paying in at a bank aren’t.

Miss the 31 January 2027 deadline for filing and a £100 penalty lands the next day. Miss the payment part and late payment penalties and interest start running separately.

31 July 2027: second payment on account for 2026/27

If you made a first payment on account in January, the second instalment for 2026/27 is due by 31 July 2027. It’s normally the same amount as the first.

That’s a Saturday, so the same weekend rule applies: unless you use Faster Payments or a card, the money needs to arrive by Friday 30 July 2027. HMRC charges interest on any payment that’s late.

Missed the 5 October registration deadline? What changes

Register now. HMRC then issues a notice telling you when your return is due. GOV.UK’s summary describes it as three months from the notice, but HMRC’s manual gives the full rule: for an online return, it’s 31 January 2027 or three months from the date of the notice, whichever is later.

Your payment date doesn’t move with it. The tax for 2025/26 is still due by 11:59pm on 31 January 2027, whatever your filing date says.

That payment date is also what HMRC’s failure to notify penalty turns on. You may get one if you registered after 5 October and haven’t paid your whole 2025/26 bill by 31 January 2027, and it’s worked out from the amount still unpaid. Pay everything by then and the condition for that penalty isn’t met.

Until your return is in, HMRC’s Self Assessment tax calculator on GOV.UK will estimate your 2025/26 Income Tax and Class 4 National Insurance.

The guide on how to register for Self Assessment covers the sign-up steps.

Payment on account dates: why January bills jump

Payments on account mean paying part of your next tax bill early: one instalment by 31 January and another by 31 July. Each instalment is usually 50% of the previous year’s tax.

You won’t be asked for them if either of these applies:

• Your Self Assessment tax for the previous year came to less than £1,000.
• More than 80% of last year’s tax was already collected another way, such as through your tax code or deducted by your bank from savings interest.

Your balancing payment also picks up anything owed for capital gains, and for student loans if you’re self-employed.

A worked example: the first-year jump

Take a sole trader whose 2025/26 bill comes to £4,800, with no tax collected through PAYE and no payments on account made before.

On 31 January 2027 they pay the £4,800 balancing payment plus a £2,400 first payment on account for 2026/27: £7,200 in one go. Another £2,400 follows on 31 July 2027.

That’s £9,600 inside six months, of which £4,800 is paid in advance for 2026/27. If their 2026/27 bill also comes to £4,800, the balancing payment due on 31 January 2028 is nil, and the first payment on account for 2027/28 (£2,400) is due that day instead.

If you know your 2026/27 tax will come in lower than last year’s, you can ask to reduce the instalments, either online through your Self Assessment account or by posting form SA303 to HMRC. Set them too low and HMRC charges interest on the difference once your real bill is known.

Self Assessment late filing penalties start the next day

Filing late and paying late are penalised separately. Miss 31 January 2027 with both the return and the money, and two sets of charges start at once.

For a late return, the Self Assessment late filing penalty builds up like this:

• One day late, there’s a fixed £100 penalty, even when nothing is owed.
• At three months late, £10 a day is added, up to a maximum of £900.
• At six months late, HMRC adds the greater of £300 and 5% of the tax due.
• At twelve months late, it adds the greater of £300 and 5% again.

Unpaid tax is charged 5% of the amount outstanding at 30 days, again at six months and again at 12 months. HMRC also charges interest on what’s owed; the rate changes from time to time, so check the current figure on GOV.UK rather than relying on one quoted in an article.

To see how it adds up, take a £3,500 bill where the return and the money are both a year late.

The filing penalties come to £1,600 (£100, £900 and two lots of £300, because 5% of £3,500 is only £175). The three late payment charges are £175 each, another £525. That’s £2,125 before any interest.

If something genuinely prevented you from filing or paying on time, you can appeal a penalty on the grounds of a reasonable excuse.

MTD quarterly deadlines add dates, not payment days

Making Tax Digital for Income Tax (MTD) depends on your qualifying income for MTD. Since 6 April 2026 it has covered sole traders and landlords whose qualifying income in 2024/25 was over £50,000. The threshold falls to over £30,000 from April 2027, based on 2025/26 income, and to over £20,000 from April 2028.

HMRC writes to people who need to start, but if no letter arrives, checking whether you’re in is still your responsibility.

Your 2025/26 return sits outside MTD either way. Even if you joined in April 2026, that return is filed the usual way by 31 January 2027, under the current penalty rules.

If you’re in MTD now, these are your 2026/27 quarterly update deadlines:

• The update for 6 April to 5 July 2026 was due by 7 August 2026.
• The update for 6 April to 5 October 2026 is due by 7 November 2026.
• The update for 6 April 2026 to 5 January 2027 is due by 7 February 2027.
• The update for the full year to 5 April 2027 is due by 7 May 2027.

Each update is cumulative, adding up income and expenses since 6 April, and it goes to HMRC from your software. It’s a summary, not a tax return, and you don’t need to adjust the figures for accounting or tax purposes first.

For 2026/27, HMRC isn’t giving penalty points for late quarterly updates, though points still apply to a late tax return. The guidance on sending quarterly updates also covers calendar update periods.

Your 2026/27 tax return is still a tax return. You prepare it in MTD-compatible software and finish it with a final declaration confirming it’s complete and correct. It replaces the old SA100 return rather than coming on top of it, and it’s due by 31 January 2028.

None of this moves when you pay. Tax is still due on 31 January, with 31 July for a second payment on account.

Employing staff? The P11D deadline 2027 is 6 July

If you provide employees with taxable benefits or expenses, there’s a separate set of employer dates. Payrolling every benefit removes the need for P11D forms for those employees, but the P11D(b) and the Class 1A payment are still due.

The 2025/26 dates passed in July 2026. For 2026/27 benefits, the next set is:

• By 6 July 2027, report the expenses and benefits to HMRC on P11D and P11D(b), give each employee a copy of their information, and report how much Class 1A National Insurance is due.
• By 22 July 2027, pay that Class 1A National Insurance electronically.
• By 19 July 2027, pay it instead if you’re paying by cheque.

A late P11D(b) costs £100 for each 50 employees, for every month or part month it’s late. The employer deadlines on GOV.UK also list the dates for PAYE Settlement Agreements.

Self Assessment deadlines 2026/27 follow the same pattern

Roll every date forward a year and you have the next cycle. For income earned between 6 April 2026 and 5 April 2027:

• New filers register by 5 October 2027.
• Paper returns are due by 31 October 2027, for anyone not in MTD.
• Online returns are due by 31 January 2028, along with whatever’s left to pay for 2026/27 and the opening instalment for 2027/28.
• The July instalment for 2027/28 lands on 31 July 2028.

The two payments on account for 2026/27 itself fall on 31 January 2027 and 31 July 2027, inside the 2025/26 cycle above. That overlap is why one January payment can cover two tax years.

Filing doesn’t always end in a bill, either. Where you’ve overpaid, a refund may be possible, though if you’ve got tax due within the next 45 days, HMRC may take the refund off that instead of paying it out. Check whether you’re due a tax rebate.

Your next step on Self Assessment deadlines 2025/26

Work out which of the Self Assessment deadlines 2025/26 apply to you, then put them in your calendar. If you file online, 31 January 2027 is the date that matters: file, pay what you owe, and make a first payment on account if you’re in that system.

It’s a Sunday, so slower payment methods need to arrive by Friday 29 January. Online filers who want to pay through their tax code have until 30 December 2026, and paper returns are due earlier, by 31 October 2026.

Registered late? Your filing date may move, but the payment date doesn’t. MTD changes how you report from 2026/27, not when you pay. The Self Assessment tax return guide covers the return itself.

Key takeaways

• The 2025/26 tax year ended on 5 April 2026, so file online by 31 January 2027, or get a paper return to HMRC by 31 October 2026.
• Tax owed for 2025/26 has to reach HMRC by 31 January 2027, and because that’s a Sunday, slower payment methods need to arrive by Friday 29 January.
• If you registered after 5 October 2026, your filing deadline depends on when HMRC issues your notice to file, but your payment date stays at 31 January 2027.
• Payments on account, each usually half of last year’s tax, are due on 31 January and 31 July, unless last year’s bill was under £1,000 or more than 80% of it was collected another way.
• MTD quarterly updates for 2026/27 are summaries rather than tax returns, and the 2026/27 tax return under MTD is due by 31 January 2028.