When is your Self Assessment Tax Return due in the UK?

Also, a quick heads-up: from April 2026, the rules will start to change under Making Tax Digital for Income Tax Self Assessment (MTD ITSA). This means many sole traders and landlords will begin sending quarterly digital updates to HMRC instead of one annual return. But until then, Self Assessment remains the way to report your income - so let’s walk through how it works now, and when everything is due.

It’s also worth remembering that if you use ANNA business account you’ll get early reminders of all your deadlines, as well as help getting your accounts into shape, so filing your Self Assessment is a breeze.

Now let’s take a look at the dates in more detail.

Self Assessment due dates in the UK: what “due” actually means

Paying taxes is rarely simple, and there’s some scope for confusion. When people ask “When is Self Assessment due?”, they could mean two slightly different things:

• The filing due date: when your tax return must be submitted.
• The payment due date: when the tax you owe has to be paid.

Self Assessment due dates at a glance

Here’s a quick run-through of the main Self Assessment deadlines in the UK, and what each one means for you.

6 April: start of the new tax year

Some things are consistent, and one of them is the tax year. The UK tax year runs from 6 April to 5 April. Income earned from 6 April onwards counts towards the new tax year.

5 April: end of the tax year

The tax year ends on 5 April. The return you file covers income from the previous 12 months ending on this date.

5 October: deadline to register for Self Assessment

If you’re newly self-employed, started earning rental income, or otherwise need to file a tax return for the first time, you must register by 5 October after the end of the tax year.

For example, if you started trading in June 2024, you’ll need to register by 5 October 2025.

31 October: paper tax return filing deadline

If you’re submitting a paper tax return, HMRC must receive it by 31 October following the end of the tax year. Very few people use paper now, as online filing gives you more time and flexibility.

30 December: online filing deadline to code out underpaid tax via PAYE

If you’re employed and owe less than £3,000, you can ask HMRC to collect the tax through your PAYE code next year - but only if you file online by 30 December.

31 January: online tax return filing deadline

For most people, 31 January is the big date: your online Self Assessment tax return for the previous tax year has to be filed by midnight (yes, the midnight deadline does make it sound quite spooky).

31 January: balancing payment and first payment on account due

This is also when your balancing payment is due (the tax you owe for the year just ended). If you make payments on account, your first instalment for the current tax year is also due on 31 January.

Payments on account are advance payments towards your next year’s tax bill, made in two installments (31 January and 31 July) based on your previous year’s tax.

31 July: second payment on account due

If applicable, your second payment on account for the current tax year is due by 31 July.

When you sign up to ANNA +Taxes, you get your own personalised tax calendar with all the important dates (including Self Assessment) and we remind you of your obligations so you never miss a deadline again.

Which Self Assessment is due now? (what year is due and when)

Each Self Assessment return covers one specific tax year - and it’s always the previous year that you’re filing for.

Example: the 2024/25 tax year

Covers income from 6 April 2024 to 5 April 2025.
Your online return and payment are due by 31 January 2026.

Example: the 2025/26 tax year

Covers income from 6 April 2025 to 5 April 2026.

Key dates:

• Register by 5 October 2026
• Paper return due 31 October 2026
• Online return and payment due 31 January 2027

Registering for Self Assessment (do this by 5 October)

You’ll need to register if:

• You’re self-employed as a sole trader and earned over £1,000.
• You’re a landlord receiving rental income.
• You receive significant untaxed income (for example, savings interest or dividends).
• You need to pay the High Income Child Benefit Charge.

You can register online through GOV.UK. HMRC will send you a Unique Taxpayer Reference (UTR). This can take up to two weeks, so don’t leave it too late.

If you miss the 5 October deadline, register as soon as you can. HMRC can issue penalties, but acting quickly can help show you’ve made an effort to comply.

Filing your Self Assessment tax return: methods and timing

You can file your tax return online or on paper.

• Online filing gives you until 31 January, instant submission confirmation, and easier amendments.
• Paper returns have to arrive by 31 October and take longer to process.

If you don’t yet know your final figures, you can use provisional numbers - just make sure you update them once your records are complete.

Partnerships and trusts have their own versions of Self Assessment, with slightly different forms and sometimes earlier deadlines.

If you’re an ANNA customer you can file your Self Assessment tax return through us. We’ll prepare your tax return, and make sure you’re claiming all your expenses, so all you have to do is review the return and click to submit it!

Paying your Self Assessment tax bill: when is payment due?

Your Self Assessment tax payment is due by 31 January each year. This includes:

• The balancing payment for the previous tax year.
• The first payment on account (if applicable) for the current tax year.

If your tax bill is over £1,000 and less than 80% of your tax is collected via PAYE, HMRC assumes you’ll continue earning at a similar level and asks for two payments on account (on 31 January and 31 July).

Reducing or increasing payments on account

If you expect to earn less this year, you can ask HMRC to reduce your payments. Be careful though: if you reduce them too far, you’ll owe interest later.

The first-year “payment shock”

Your first Self Assessment payment can feel high – because you’re paying for last year and half of this year at once. You can budget ahead to soften the blow (if you use ANNA, you can create a pot for saving into, to cover your tax bill and your payment on account).

Class 2 and Class 4 National Insurance

If you’re self-employed, your Class 2 and Class 4 NICs are usually included in your Self Assessment calculation and due at the same time as your tax bill.

PAYE coding out option (file by 30 December)

If you’re employed and owe less than £3,000, you can ask HMRC to collect the tax through your PAYE tax code - spreading it across your payslips for the next year. To use this option, your online return must be filed by 30 December.

How to pay HMRC and when payments clear

You can pay HMRC in several ways:

• Faster Payments or debit card: usually clears the same day.
• CHAPS: same day if sent before your bank’s cut-off time.
• Bacs: takes three working days.
• By bank or building society (with payslip): also three days.

Always use your 11-character payment reference (from your HMRC statement) so the payment is applied correctly. If the deadline falls on a weekend or bank holiday, make sure your payment clears before the next working day.

Late filing and late payment: penalties, surcharges and interest

If you file or pay late, HMRC applies:

• £100 penalty if you’re up to 3 months late.
• Daily penalties after 3 months (up to £900).
• 6-and 12-month penalties based on the tax due.
• Interest charged daily on late payments.

If you can’t pay, you can apply for a Time to Pay arrangement to spread the cost. Interest still applies, but it helps you avoid larger penalties.

Amending a return, refunds and claims

If you spot an error after filing, you can amend your return within 12 months of the original deadline.If you’ve overpaid tax, you can claim a refund online through your HMRC account.

Make sure you keep all records and evidence in case HMRC asks for more details.

Record-keeping and timelines behind the deadlines

You have to keep records for at least 5 years after the 31 January filing deadline, including:

• Invoices and receipts
• Bank statements
• Mileage logs (if relevant)
• Dividend vouchers and property records

This helps you file accurately and prove your figures are correct if HMRC ever checks.

ANNA stores all your business documents safely and securely in the cloud, so you never have to go hunting through shoeboxes or old emails to find your paperwork.

Planning ahead so you never miss a Self Assessment due date

A few simple habits make Self Assessment a lot less stressful:

• Add deadlines to your calendar - ANNA can remind you when they’re coming up.
• Set aside tax money regularly - around 20–30% of income is a good rule of thumb. You can use an ANNA pot to put aside money for your Self Assessment tax bill.
• File early - you’ll know what you owe and can plan your payments.

The bottom line

Self Assessment may feel like a long list of dates, but once you understand the rhythm, it becomes much easier to manage.

And with Making Tax Digital (MTD for ITSA) on the horizon, getting organised now will make the shift to quarterly updates far smoother later.

ANNA can help you keep your records, reminders, and payments running smoothly - so when tax time comes around, you’re already halfway there.