Self Assessment Tax Return Deadlines 2025-26: Register, File & Pay
Self Assessment is HMRC's system for collecting tax from people whose income is not taxed automatically through PAYE. If you need to complete a Self Assessment return for the 2024-25 tax year, the filing and payment deadlines are in the months ahead. Missing them triggers automatic penalties that accumulate quickly.
Who needs to file a Self Assessment return?
You generally need to complete Self Assessment if, in the 2024-25 tax year, you:
- Were self-employed with income above £1,000
- Earned more than £100,000 in total income
- Received income from renting out property
- Had untaxed income of more than £2,500 (savings interest, dividends, etc.)
- Were a company director
- Had a High Income Child Benefit Charge to pay
- Received income from abroad
Key deadlines for the 2024-25 return
| Deadline | What it covers |
|---|---|
| 5 October 2025 | Register for Self Assessment (first-time filers only) |
| 31 October 2025 | Submit paper Self Assessment return for 2024-25 |
| 31 January 2026 | Submit online return for 2024-25 AND pay any tax owed AND pay first payment on account for 2025-26 |
| 31 July 2025 | Second payment on account for 2024-25 (based on 2023-24 bill) |
Penalties for missing deadlines
HMRC's late filing penalties are automatic:
- Day 1 after deadline: £100 fixed penalty, even if no tax is owed
- 3 months late: Additional £10 per day, up to a maximum of £900
- 6 months late: 5% of tax owed or £300, whichever is greater
- 12 months late: A further 5% of tax owed or £300, whichever is greater
Interest accrues on unpaid tax from 31 January 2026, currently at HMRC's standard rate (Bank Rate + 2.5%).
Payment on account explained
If your Self Assessment tax bill exceeds £1,000, HMRC requires you to make advance payments toward the following year's bill. Each payment on account is 50% of your previous year's tax bill. These are due 31 January and 31 July. If your income changes significantly, you can apply to reduce payments on account — but if you reduce them too much you will owe interest on the shortfall.
Frequently asked questions
Can I file Self Assessment online if I've never done it before?
Yes, but you need to register first at gov.uk/register-for-self-assessment. HMRC will post you a Unique Taxpayer Reference (UTR) within 10 working days, and then you can activate your account online. Allow time for this process before the 31 January deadline.
What if I can't pay by the deadline?
Contact HMRC before the deadline, not after. HMRC offers Time to Pay arrangements that allow you to spread payment in instalments. Penalties may still apply but interest is charged at a lower rate than the default.