What is due on 31 January 2027
By 11:59pm on 31 January 2027 you need to:
- File your 2025/26 return online. It covers 6 April 2025 to 5 April 2026. The paper deadline (31 October 2026) has passed.
- Pay the rest of your 2025/26 tax (the balancing payment), including Class 4 National Insurance and any student loan repayments.
- Pay your first payment on account for 2026/27, if your bill is £1,000 or more and less than 80% of your tax was taken at source.
If you registered for Self Assessment after 5 October 2026, HMRC gives you three months from the date on its letter to file, but the tax is still due on 31 January 2027.
What to gather before you start
- Your login and UTR. Your Government Gateway or One Login details and your 10-digit Unique Taxpayer Reference. If you have lost them, sort it now: new codes come by post and can take days.
- Your income for 2025/26. Every sale, invoice and payment from 6 April 2025 to 5 April 2026, including selling apps and platforms. Platforms such as Etsy, Vinted, eBay and Airbnb now report sellers to HMRC, so your figures should match theirs.
- Your expenses, by type. Stock, tools, phone, insurance, software, advertising, travel. Keep receipts: HMRC can ask for them for years.
- Your mileage log if you drive for work, and your use-of-home hours if you work from home.
- Any job or pension: your P60 (or P45) and any P11D benefits.
- Other income: bank and savings interest, dividends, rent, CIS statements if you are a subcontractor.
- Things that change your bill: pension contributions, Gift Aid donations, Child Benefit if anyone in the house earns over £60,000, and your student loan plan type.
Use the 2025/26 figures, not this year's
The most common slip in January is using today's figures on last year's return. For 2025/26:
| Item | 2025/26 |
|---|---|
| Personal allowance | £12,570 |
| Income tax (England, Wales, NI) | 20% up to £50,270, 40% up to £125,140, 45% above |
| Class 4 National Insurance | 6% on profits £12,570 to £50,270, 2% above |
| Class 2 National Insurance | Nothing to pay. Profits of £6,845 or more count for your State Pension; below that you can pay £3.50 a week voluntarily |
| Mileage (cars and vans) | 45p a mile for the first 10,000 business miles, then 25p |
| Trading allowance | £1,000 |
| Working from home (flat rate) | £10, £18 or £26 a month for 25 to 50, 51 to 100, or 101+ hours |
Watch the mileage rate. The 55p rate started on 6 April 2026, so it belongs on next year's return, not this one. Scotland has its own income tax bands; Class 4 NI is the same across the UK.
The payments on account surprise
If your 2025/26 bill is £1,000 or more, HMRC usually asks for two advance payments towards 2026/27, each half of this year's bill: one on 31 January 2027 and one on 31 July 2027. In your first year that means paying one and a half times your bill in January.
Example: a £4,000 bill for 2025/26 means £6,000 on 31 January 2027 (the £4,000 plus a £2,000 payment on account) and £2,000 on 31 July 2027. If your income has dropped, you can ask HMRC to reduce them.
See your own figures with the payments on account calculator.
If you cannot pay it all
- File on time anyway. The £100 late filing penalty applies even if you cannot pay.
- Owe less than £3,000 and have a job or pension? File online by 30 December 2026 and HMRC can collect it through your tax code over 2027/28 instead of in one go.
- Pay in smaller amounts before the deadline. You can pay towards your bill early, for example monthly, through GOV.UK or the HMRC app, as long as it is cleared by 31 January.
- Set up a payment plan. Once you have filed, you can spread a bill of up to £30,000 online. Agree it before the 30-day point to avoid the 5% late payment penalty. Interest still runs.
- Use the right reference. Pay using your UTR followed by the letter K, so the money lands in the right place.
If you miss the deadline
The 2025/26 return is under the current penalty rules for most people:
| How late | Filing late | Paying late |
|---|---|---|
| 1 day | £100 | Interest starts (7.75% a year) |
| 30 days | 5% of the tax unpaid | |
| 3 months | £10 a day, up to £900 | |
| 6 months | £300 or 5% of the tax, whichever is higher | Another 5% |
| 12 months | Another £300 or 5% | Another 5% |
If something serious stopped you, such as a hospital stay or a bereavement, you can appeal with a reasonable excuse. If you joined Making Tax Digital voluntarily for 2025/26, the new points-based penalties apply to you instead. They apply to everyone from the 2027/28 tax year.
After you file: get 2026/27 sorted
Once January is done, make next year easier. For 2026/27, use 55p a mile for your first 10,000 business miles. If your income was over £50,000, Making Tax Digital quarterly updates started in April 2026; over £30,000, they start in April 2027 (you still file the 2025/26 return the usual way). Keep your records as you go and put money aside each month. Our free tax set-aside calculator works out how much.
Sources: GOV.UK guidance on Self Assessment deadlines, payments on account, paying through your tax code, payment plans, penalties and HMRC interest rates; HMRC's 2025/26 rates and allowances. This page explains the rules in plain English and is not tax advice.