Self Assessment Deadlines 2025-26: Filing and Payment Dates
The key deadlines for the 2025-26 tax year: paper returns by 31 October 2026, online returns by 31 January 2027. Missing these dates triggers automatic penalties starting at £100.
Who Needs to File a Self Assessment Return?
You must file a Self Assessment return if any of the following apply in the 2025-26 tax year:
- You are self-employed or a sole trader with business income
- You are a company director (unless the company is non-profit and you received no pay or benefits)
- Your income was above £100,000 in the year
- You have untaxed income above £2,500 (e.g. rental income, freelance earnings, tips)
- You have income from savings or investments above your annual allowances
- You have foreign income that needs to be reported
- You need to claim certain tax reliefs (such as pension contributions above your employer's scheme)
- You or your partner receive Child Benefit and either of you earns above £60,000 (High Income Child Benefit Charge)
- You have Capital Gains above the annual exempt amount
Key Dates and Deadlines
| Date | What Is Due |
|---|---|
| 5 April 2025 | 2024-25 tax year ends |
| 31 July 2025 | Second Payment on Account for 2024-25 |
| 5 October 2025 | Deadline to register for Self Assessment for 2024-25 |
| 31 October 2025 | Paper return deadline for 2024-25 tax year |
| 31 January 2026 | Online return for 2024-25 + balancing payment + First POA for 2025-26 |
| 5 April 2026 | 2025-26 tax year ends |
| 31 July 2026 | Second Payment on Account for 2025-26 |
| 5 October 2026 | Deadline to register for Self Assessment for 2025-26 |
| 31 October 2026 | Paper return deadline for 2025-26 tax year |
| 31 January 2027 | Online return for 2025-26 + balancing payment + First POA for 2026-27 |
Payments on Account (POA)
Payments on Account are advance payments towards your next year's tax bill. HMRC requires them when:
- Your Self Assessment tax bill (excluding Capital Gains Tax) is more than £1,000, and
- More than 20% of your tax was not deducted at source (e.g. through PAYE)
Each Payment on Account equals 50% of the previous year's tax bill. There are two payments per year — one on 31 January and one on 31 July.
If you expect your income to be lower in the current year, you can apply to HMRC to reduce your Payments on Account. If you reduce them by too much, HMRC will charge interest on the underpayment.
Late Filing Penalties
| How Late | Penalty |
|---|---|
| 1 day late | Automatic £100 fine (applies even if no tax is owed) |
| 3 months late | Additional £10 per day for up to 90 days (maximum £900) |
| 6 months late | Additional £300 or 5% of tax due, whichever is higher |
| 12 months late | Additional £300 or 5% of tax due — higher penalties for deliberate withholding |
Late Payment Penalties
Separate penalties apply if you file on time but pay your tax late:
| Payment Delay | Penalty |
|---|---|
| 30 days late | 5% of unpaid tax |
| 6 months late | Additional 5% of unpaid tax still outstanding |
| 12 months late | Additional 5% of unpaid tax still outstanding |
In addition to penalties, HMRC charges interest on all late payments. From April 2025, the interest rate is Bank Rate plus 2.5%, which is approximately 7.25% per year. Interest accrues daily from the date the payment was due.
How to Register for Self Assessment
If this is your first time filing, you must register with HMRC before you can submit a return. The registration deadline is 5 October following the end of the relevant tax year — so 5 October 2026 for the 2025-26 tax year.
After registering online, HMRC will send your Unique Taxpayer Reference (UTR) by post within about 10 working days. You will also need to set up a Government Gateway account to file online. Allow sufficient time — do not wait until the last week of January to begin this process.
Frequently Asked Questions
What happens if I miss the 31 January deadline?
You receive an automatic £100 penalty the day after the deadline, even if you owe no tax. If the return is 3 months late, HMRC adds £10 per day (up to 90 days, maximum £900). At 6 months, a further £300 or 5% of tax owed is added. Late payment of the tax itself also attracts separate penalties starting at 5% after 30 days, plus daily interest.
Do I need to file if I am PAYE?
Most PAYE employees do not need to file. However, you must file if you have income above £100,000, untaxed income above £2,500, income from abroad, or if HMRC has sent you a notice to file. If in doubt, check your HMRC personal tax account.
How do I register for Self Assessment?
Register online through your HMRC account or the GOV.UK website. Self-employed individuals register as sole traders. You must register by 5 October following the tax year you started — so 5 October 2026 for the 2025-26 tax year. You will receive a UTR number by post, which you need to file your return.
Use our Self Assessment calculator to estimate your tax bill and Payments on Account.