Self Assessment deadline 31 January 2027: what you need to know
If you're self-employed, a landlord or have other untaxed income, your 2025/26 tax return must be filed online by 31 January 2027. Here's everything you need to know to get it done on time.
Which tax year does this cover?
The return due on 31 January 2027 covers the 2025/26 tax year, which ran from 6 April 2025 to 5 April 2026. Any income you received in that period, from self-employment, property, dividends or other untaxed sources, goes on this return.
Key Self Assessment dates
| Date | What's due |
|---|---|
| 5 October 2026 | Deadline to register for Self Assessment if you needed to file for the first time for 2025/26 |
| 31 October 2026 | Deadline for paper tax returns |
| 31 January 2027 | Deadline for online tax returns, and to pay any tax you owe for 2025/26 plus your first payment on account for 2026/27 |
| 31 July 2027 | Second payment on account for 2026/27 |
If you missed the 5 October registration deadline, don't panic. Register as soon as possible and still aim to file by 31 January.
Who needs to file a tax return?
You'll usually need to file if, during the tax year, you:
- were self-employed and earned more than £1,000 (the trading allowance) before expenses
- were a partner in a business partnership
- had rental income from property
- had untaxed income, such as tips, commission or income from abroad
- were a company director with income not taxed through PAYE
- had to pay the High Income Child Benefit Charge, if not paying it through PAYE
Not sure if this applies to you? Ask us and we'll tell you.
What happens if you miss the deadline?
HMRC's penalties for a late return add up quickly, even if you don't owe any tax:
- £100 as soon as your return is late
- after 3 months, £10 a day for up to 90 days (up to £900)
- after 6 months, a further £300 or 5% of the tax due, whichever is higher
- after 12 months, another £300 or 5%, whichever is higher
Separate penalties and interest apply if you pay your tax late, so it pays to file and pay on time.
What are payments on account?
If your Self Assessment bill is more than £1,000, and less than 80% of your tax is already taken at source (for example through PAYE), HMRC usually asks you to pay towards next year's bill in advance. These are called payments on account.
Each one is normally half of the previous year's bill, due on 31 January and 31 July. This can come as a shock in your first year of self-employment, because in January you may have to pay your full first year's bill plus half as much again. If you expect your income to fall, you can apply to reduce your payments on account.
Tip: set aside around 20% to 30% of your profits in a separate savings account throughout the year, so the January bill never comes as a surprise.
What you'll need
- your Unique Taxpayer Reference (UTR) and National Insurance number
- records of your business income and expenses for the year
- details of any rental income and costs
- P60s or P45s from any employment
- bank or building society interest, and dividends
- pension contributions and Gift Aid donations
How to avoid the January rush
Thousands of people file in the last week of January, when HMRC's phone lines are at their busiest. Getting your records together in November or December means you'll know your bill early, have time to budget for it, and won't miss expenses you could have claimed.
Our Self Assessment service is £24.95 a month + VAT, or £249 + VAT as a one-off. We prepare and file your return, make sure every allowable expense is claimed, and remind you well before each deadline.
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This article is general guidance based on the rules in place when it was written (October 2026). Tax rules change and everyone's situation is different, so please speak to us before making decisions.