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Self Assessment Tax Return Deadline 2026/27: What You Need to Know
The next Self Assessment deadline is 31 January 2027. That's when your online return for the 2025/26 tax year is due, and when you pay the tax you owe.
Here's what it covers, the other dates around it, what missing it costs, and how to be ready well before January.
By Rehan Razzaq FCCA · Published · Updated · 6 min read
The short answer
- 31 January 2027: file your 2025/26 return online and pay what you owe.
- 31 October 2026: the deadline if you file on paper.
- 5 October 2026: register for Self Assessment if 2025/26 was your first year.
- Miss it: a £100 penalty straight away, even if you owe no tax, and more the longer it runs.
All dates and penalties in this article were checked against GOV.UK on 1 October 2026.
Which tax year does this deadline actually cover?
This trips almost everyone up. The return due by 31 January 2027 covers the 2025/26 tax year, from 6 April 2025 to 5 April 2026.
It doesn't cover the 2026/27 tax year you're trading through now. That return isn't due until 31 January 2028. So the records you need now are the ones for the year that ended on 5 April 2026.
What are the key dates for the 2025/26 tax year?
- 5 October 2026: register for Self Assessment if you started self-employment or renting out property in 2025/26 and haven't registered before
- 31 October 2026: deadline for paper returns
- 30 December 2026: file online by this date if you want a bill under £3,000 collected through your PAYE tax code
- 31 January 2027: deadline for online returns, and to pay the tax you owe plus your first payment on account for 2026/27, if one applies
- 31 July 2027: second payment on account, if one applies
These come from HMRC's Self Assessment deadlines page. If you register after 5 October, HMRC gives you 3 months from the date it tells you to file, but the tax is still due by 31 January.
Most people file online, which gives you three more months than paper.
What happens if you miss the Self Assessment deadline?
Late filing penalties apply even if you don't owe any tax:
- 1 day late: an automatic £100 penalty
- 3 months late: £10 a day, up to a maximum of £900
- 6 months late: a further 5% of the tax due or £300, whichever is greater
- 12 months late: another 5% of the tax due or £300, whichever is greater
Paying late is charged separately. HMRC adds a penalty of 5% of the unpaid tax at 30 days, 6 months and 12 months, plus interest on the amount owed.
Both sets of penalties are on HMRC's page on Self Assessment penalties. In our experience, almost every late filing comes down to disorganised records, not a complicated tax position.
How can you be ready before January rather than in it?
The people who find January stressful are usually trying to rebuild a year of records in its first three weeks. A few things make a real difference if you do them now:
- Pull together bank statements, invoices and receipts for the full 2025/26 tax year while it's still recent
- Check you've registered for Self Assessment, if 2025/26 was your first year of self-employment or rental income
- Work out roughly what you'll owe early, so a payment on account for 2026/27 isn't a surprise on top of your bill
- If your records are already a mess, our bookkeeping service can sort them before they become a filing problem
The bottom line
The deadline is the same handful of dates every year: 5 October to register, 31 October on paper, 31 January online and to pay. What causes problems is leaving the records until January, not the filing itself.
How REYS Accountants can help
We're a small practice in Catford, SE6, and Self Assessment returns are a large part of our work every January.
Our Self Assessment service prepares and files your return, works out what you owe well ahead of 31 January, and explains the number in plain English before anything goes to HMRC.
Landlords should see our page on rental income tax in Brockley and Ladywell, and employees with extra income should see personal tax for higher earners in Forest Hill and Honor Oak. Behind on registering? Get in touch and we'll tell you straight where you stand.
Frequently Asked Questions
31 October 2026 if you file a paper return, or 31 January 2027 if you file online. Any tax you owe for the year is also due by 31 January 2027, along with your first payment on account for the following year if one applies.
HMRC charges an automatic £100 penalty, even if you don't owe any tax. After 3 months, £10 a day can apply up to £900, with further penalties at 6 and 12 months. Paying late adds separate 5% penalties and interest.
By 5 October following the end of the tax year you need to file for. If you started self-employment or began renting out a property during the 2025/26 tax year, you need to register with HMRC by 5 October 2026.
Filing on time with your best figures is usually better than missing the deadline. You can correct a return within 12 months of the deadline. Getting your records in order early is the real fix, and we can help you sort them before January.
If your self-employment and property income was over £50,000 on your 2024/25 return, Making Tax Digital for Income Tax has applied since 6 April 2026. The threshold falls to £30,000 from April 2027 and £20,000 from April 2028. Check HMRC's eligibility guidance.
This article is general guidance for UK businesses and individuals and does not constitute personal tax advice. Figures and rules are as published on GOV.UK at 1 October 2026, and any examples are illustrative. Rates, thresholds and individual circumstances vary and can change, so always confirm your specific position with a qualified accountant or on GOV.UK before acting.
Behind on your records already?
Book a short call and we'll tell you exactly what's needed before January, no pressure, no obligation.
Book a short callDeadline: 31 January 2027