Who Needs to File a Self-Assessment Tax Return?
In the UK, you typically need to file a Self Assessment tax return if you have a source of income that isn't taxed automatically through the Pay As You Earn (PAYE) system. Individuals and certain businesses must complete a tax return each year to declare their income and gains so that HMRC can check that they are meeting their income tax obligations. If you’re unsure whether you need to file, what deadlines apply, or what happens if you don’t comply, this guide will help.
You can also download a helpful printable checklist to make sure you are fully prepared and have completed all the stages of the system. Download checklist
You may need to complete a tax return if, in the last tax year (6 April – 5 April), you:
- Were self-employed as a sole trader and earned more than £1,000 before expenses.
- Were a partner in a business partnership.
- Received rental income as a landlord.
- Had untaxed income, such as from investments, dividends, or savings interest.
- Earned income from abroad that is taxable in the UK.
- Had income over £100,000.
- Claimed child benefit and either you or your partner earned more than £50,000 (High Income Child Benefit Charge).
- Owed Capital Gains Tax (e.g., from selling shares, a property, or other investments).
Most employees and pensioners don’t need to file, unless they have additional income or tax circumstances that HMRC can’t deal with automatically.
Key Deadlines
- 5 October 2025 – Deadline to register for Self-Assessment (if it’s your first return).
- 31 October 2025 – Paper tax return deadline.
- 31 January 2026 – Online tax return deadline (for the 2024/25 tax year).
- 31 January 2026 – Deadline for paying any tax you owe.
- 31 July 2026 – Second payment on account deadline (if applicable).
Penalties for Late Filing or Payment
HMRC takes deadlines seriously. Missing them can lead to automatic penalties:
- Late filing
- 1 day late: £100 fine (even if you owe no tax).
- 3 months late: £10 per day (up to £900).
- 6 months late: Additional £300 (or 5% of the tax due if higher).
- 12 months late: Further £300 (or 5% of tax due if higher).
- Late payment
- 30 days late: 5% of tax due.
- 6 months late: Another 5%.
- 12 months late: A further 5%.
- Plus interest charged on unpaid tax.
How to Stay Compliant
- Check early whether you need to file a return.
- Register promptly if you’re new to Self-Assessment.
- Keep good records – invoices, receipts, bank statements, rental agreements/statements.
- Submit online – it’s quicker, easier, and gives you more time than paper returns.
- Budget for payments – don’t get caught out in January and July.
Why Professional Help Matters
The Self-Assessment system may seem straightforward, but tax rules can be complex—especially if you have multiple income sources, property, or investments. Errors or missed deadlines can be costly.
Working with an accountant means:
- Peace of mind that your return is correct and on time.
- Guidance on tax reliefs and allowances you may not know about.
- Support with HMRC if there are queries.
Next Steps: If you think you may need to file a Self-Assessment tax return this year, get in touch with us today. We can check your position, handle the filing for you, and help you avoid unnecessary penalties Contact us via email hello@richardsonswift.co.uk or via the contact form on the website or call on 01225 325580