Most UK employees pay the right amount of tax through PAYE without needing to do anything further. But for millions of people — including the self-employed, landlords, higher earners, and those with complex affairs — HMRC requires an annual Self Assessment tax return. Missing the requirement to register or file can lead to automatic penalties, even if no tax is ultimately owed.
Who Must Register for Self Assessment?
You are required to complete a Self Assessment tax return for the 2025-26 tax year if any of the following apply:
Self-Employment and Freelancing
- You were self-employed as a sole trader and your gross income from self-employment exceeded £1,000 in the tax year.
- You were a partner in a business partnership (all partners must file, regardless of profit share).
The £1,000 figure is the Trading Allowance. If your self-employment income is below this, you may not need to register — but if you have expenses you wish to claim above the allowance, you may still benefit from filing.
Property Income
- You received rental income and your gross rental income exceeded £1,000 (the Property Allowance).
- For rental income between £1,000 and £2,500, you may be able to ask HMRC to collect tax through your PAYE code rather than filing a return.
- For gross rental income above £2,500, a Self Assessment return is required.
Higher Income
- Your taxable income exceeded £150,000 in the tax year, regardless of source. HMRC requires high earners to file even if all tax is paid correctly through PAYE.
High Income Child Benefit Charge (HICBC)
- You or your partner received Child Benefit and either of you earned over £60,000 during the year. The charge is tapered between £60,000 and £80,000, and equals the full child benefit amount above £80,000.
Untaxed Income
- You received untaxed income not collected through PAYE — for example, tips, commission, or cash-in-hand payments.
Savings and Investment Income
- You received savings interest that was not taxed at source and exceeded your Personal Savings Allowance.
- You received dividend income above the £500 Dividend Allowance.
- You made capital gains above the Annual Exempt Amount (£3,000) or realised total gains above £12,000 (four times the AEA) — even if the tax due is nil after losses.
Foreign Income
- You received income from outside the UK, including foreign employment, pensions, rental income, or investments.
Trust Income
- You received income from a trust or settlement on which you owe higher rate tax.
Other Triggers
- Your PAYE tax code was wrong for a significant period and you have underpaid tax that cannot be collected through your code.
- You want to claim certain reliefs only available through Self Assessment, such as Gift Aid claims at higher rates, pension relief claims, or Marriage Allowance when no employer tax code adjustment is possible.
- You are a company director (unless the directorship is for a non-profit and you receive no income or benefits from the company).
How to Register
You must register with HMRC by 5 October following the end of the tax year if you are filing a return for the first time. For the 2025-26 tax year (ending 5 April 2026), the registration deadline is 5 October 2026.
Register online through the Government Gateway at gov.uk/register-for-self-assessment. HMRC will then send you a Unique Taxpayer Reference (UTR), which is needed to file your return.
Key Deadlines
| Deadline | Requirement |
|---|---|
| 5 October 2026 | Register for Self Assessment for 2025-26 (if first time) |
| 31 October 2026 | File paper tax return for 2025-26 |
| 31 January 2027 | File online tax return for 2025-26 |
| 31 January 2027 | Pay any tax owed for 2025-26 |
| 31 July 2027 | Second payment on account (if applicable) |
Payments on Account
If your tax bill for the year exceeds £1,000 and less than 80% of your tax is collected at source (e.g., through PAYE), HMRC requires you to make payments on account for the following year. These are advance payments, each equal to half your previous year’s tax bill, due on 31 January and 31 July.
Example: Your 2025-26 tax bill is £3,000. You must pay £3,000 by 31 January 2027, plus a first payment on account for 2026-27 of £1,500 (half of £3,000) — a total of £4,500 due in January. A second payment on account of £1,500 follows on 31 July 2027.
Penalties for Late Filing and Payment
HMRC applies automatic penalties for late returns and late payment:
| Situation | Penalty |
|---|---|
| Return filed 1 day late | £100 fixed penalty |
| Return filed 3+ months late | £10 per day (up to 90 days = £900) |
| Return filed 6+ months late | 5% of tax due (or £300 if greater) |
| Return filed 12+ months late | Further 5% of tax due (or £300 if greater) |
| Tax paid late (30 days) | 5% of tax unpaid |
| Tax paid late (6 months) | Further 5% of tax unpaid |
| Tax paid late (12 months) | Further 5% of tax unpaid |
A £100 penalty applies even if no tax is owed and the return is only one day late.
What Is Included in a Self Assessment Return?
Your tax return captures all income sources and allowances for the tax year:
- Employment income (from all employers via P60s and P11Ds)
- Self-employment profits (using the supplementary self-employment pages)
- Property income (rental income minus allowable expenses)
- Savings income (interest from banks and building societies)
- Dividends (from UK and overseas companies)
- Capital gains (sales of shares, property, and other assets)
- Pension income (state pension, private and workplace pensions)
- Foreign income
- Other income (trusts, maintenance payments, etc.)
Allowances and reliefs claimed include pension contributions (for higher rate relief), Gift Aid, trading losses, and marriage allowance.
When You Can Stop Filing
If your circumstances change and you no longer meet any of the criteria, you can ask HMRC to remove you from Self Assessment. HMRC will confirm whether you still need to file. Do not simply stop filing without confirmation — penalties will apply even if no tax is owed.
Key Takeaways
- You must file Self Assessment if you are self-employed (income over £1,000), a landlord (rental over £2,500), earn over £150,000, or receive untaxed income including dividends above £500.
- The High Income Child Benefit Charge triggers a return if either partner earns above £60,000.
- Register by 5 October, file online by 31 January, pay by 31 January.
- A £100 fixed penalty applies for returns that are even one day late — regardless of whether any tax is owed.
- Payments on account apply if your annual tax bill exceeds £1,000 and most tax is not collected at source.
Use the self-employment tax calculator to estimate your income tax, NI, and payments on account as a sole trader.