Tax year: 2026/27 | Last reviewed: 2 October 2026
The deadline for filing your 2025/26 Self Assessment tax return online is 31 January 2027. It is also the date your tax bill for 2025/26 and, for many people, the first payment on account for 2026/27 must reach HMRC. Leaving it until January is how most penalties and nasty surprises happen, so here is what to do now.
Key Self Assessment dates
- 5 October 2026: deadline to register for Self Assessment if you need to file for 2025/26 for the first time
- 31 October 2026: paper return deadline (now passed, so online filing is the only option)
- 30 December 2026: file online by this date if you want an underpayment of less than £3,000 collected through your tax code instead of paid in one go
- 31 January 2027: online filing deadline, balancing payment for 2025/26 and first payment on account for 2026/27
- 31 July 2027: second payment on account for 2026/27
You can see every date for the year in our tax deadline diary.
What to gather
- Your UTR and Government Gateway details, or authorise us as your agent
- P60, P11D and any P45s from employment
- Self-employed income and expenses for the year, ideally from bookkeeping software
- Rental income, agent statements, mortgage interest and repair costs
- Bank and building society interest, dividends and investment statements
- Pension contributions you made personally and Gift Aid donations
- Details of any assets sold, such as shares, crypto or a second property
- Child Benefit received if your income was over £60,000
Our 2025/26 personal tax return checklist takes you through each item.
Why filing early pays off
Filing early does not mean paying early. Your tax is still due on 31 January, but you know the figure months in advance, so you can plan the cash. It also gives time to claim reliefs people often miss, such as higher-rate relief on pension contributions and Gift Aid, and to reduce payments on account if your income has fallen.
Payments on account explained
If your tax bill is more than £1,000 and less than 80% of your tax was collected at source, HMRC asks for advance payments towards next year. Each payment on account is half of the previous year’s bill. In a first year of self-employment this can mean paying 150% of a year’s tax on 31 January. We explain how this works in our guide to payments on account.
Penalties for missing the deadline
- £100 as soon as the return is late, even if no tax is owed
- £10 a day for up to 90 days once the return is three months late
- A further 5% of the tax or £300 at six months, and again at twelve months
- Late payment penalties of 5% of unpaid tax at 30 days, six months and twelve months
- Late payment interest, currently 7.75% a year (Bank of England base rate plus 4%)
If you are in Making Tax Digital for Income Tax from April 2026, a new points-based penalty system applies to your 2026/27 obligations. See our MTD for Income Tax checklist.
Can’t pay in full?
File on time anyway. Filing removes the late filing penalties, and you can usually set up a Time to Pay arrangement online for bills up to £30,000. Interest still runs, but the 5% late payment penalties are avoided while the plan is kept to.
FAQs
Which tax year is due on 31 January 2027?
The 2025/26 tax year, which ran from 6 April 2025 to 5 April 2026.
Is there a penalty if I owe no tax?
Yes. The £100 late filing penalty applies even when no tax is due, which is why it is worth checking whether you still need to file at all.
How long does an accountant need?
With complete records, we can usually turn a straightforward return round in a couple of weeks. In January, capacity is tight, so getting your records to us before Christmas is the safest plan. See our tax return service in Haywards Heath and late tax return help.
Talk it through with Digivolve
Send us your records before Christmas and we will file your 2025/26 return well ahead of 31 January, with your tax bill confirmed in writing.
This article is general information based on the rules for the 2026/27 tax year as at October 2026. It is not personal tax advice. Rates and thresholds can change, so please speak to us before acting.