The Self Assessment deadline for online tax returns is 31 January following the end of the tax year. For the 2024/25 tax year (6 April 2024 – 5 April 2025), file your online return and pay any tax owed by 31 January 2026. Missing this deadline triggers automatic penalties starting at £100.
This guide lists all key Self Assessment dates and what happens if you're late.
Key Deadlines for 2024/25 Tax Year
| Date | Deadline | |------|----------| | 5 October 2025 | Register for Self Assessment (if new) | | 31 October 2025 | Paper tax return deadline | | 30 December 2025 | File online to have tax collected via PAYE (if under £3,000 owed) | | 31 January 2026 | Online tax return deadline | | 31 January 2026 | Pay tax owed for 2024/25 | | 31 January 2026 | First payment on account for 2025/26 | | 31 July 2026 | Second payment on account for 2025/26 |
Understanding the Tax Year
The UK tax year runs from 6 April to 5 April:
| Tax Year | Period | Filing Deadline | |----------|--------|-----------------| | 2023/24 | 6 Apr 2023 – 5 Apr 2024 | 31 Jan 2025 | | 2024/25 | 6 Apr 2024 – 5 Apr 2025 | 31 Jan 2026 | | 2025/26 | 6 Apr 2025 – 5 Apr 2026 | 31 Jan 2027 |
You always file for the previous tax year. In January 2026, you're filing for income earned between April 2024 and April 2025.
Registration Deadline
5 October
If you need to file Self Assessment for the first time, register with HMRC by 5 October following the tax year.
| When You Started | Tax Year | Registration Deadline | |------------------|----------|----------------------| | June 2024 | 2024/25 | 5 October 2025 | | January 2025 | 2024/25 | 5 October 2025 | | September 2025 | 2025/26 | 5 October 2026 |
Why this matters: HMRC posts your UTR (Unique Taxpayer Reference) within 10 working days. Register late, and you may not have your UTR in time to file by 31 January.
Register at: gov.uk/register-for-self-assessment
Learn more: Self Assessment Registration Guide
Paper Return Deadline
31 October
If you file a paper tax return, the deadline is 31 October—three months earlier than online.
| Return Type | Deadline | |-------------|----------| | Paper | 31 October | | Online | 31 January |
Recommendation: File online. It's faster, you get an extra 3 months, and HMRC calculates your tax automatically.
Online Return Deadline
31 January
The main deadline most people follow. File your online Self Assessment return by 31 January following the tax year.
| Tax Year | Online Deadline | |----------|-----------------| | 2024/25 | 31 January 2026 | | 2025/26 | 31 January 2027 |
What counts as filed: Your return is filed when HMRC receives it, not when you start it. Don't leave it until 11:59pm on 31 January—technical issues could make you late.
Payment Deadline
31 January
Tax owed for the previous year is due by 31 January—the same date as the filing deadline.
| What's Due | Deadline | |------------|----------| | Tax for 2024/25 | 31 January 2026 | | First payment on account for 2025/26 | 31 January 2026 |
Important: If your tax bill exceeds £1,000, you also pay your first payment on account for the following year on 31 January.
Learn more: Payment on Account Explained
Payment on Account Deadlines
If you owe payments on account, there are two deadlines:
| Payment | Deadline | Amount | |---------|----------|--------| | First payment on account | 31 January | 50% of previous year's bill | | Second payment on account | 31 July | 50% of previous year's bill |
31 July
The second payment on account is due 31 July—6 months after the first.
Example for 2025/26:
- 31 January 2026: Pay 2024/25 tax + first payment on account
- 31 July 2026: Pay second payment on account
PAYE Tax Code Deadline
30 December
If you want HMRC to collect tax owed (up to £3,000) through your PAYE tax code the following year, file by 30 December.
| File By | Result | |---------|--------| | 30 December 2025 | Tax collected via 2026/27 PAYE code | | 31 January 2026 | Must pay in full by 31 January |
This only applies if:
- You're employed (have a PAYE income)
- You owe less than £3,000
- You file early enough
Complete Deadline Calendar
October 2025
| Date | Event | |------|-------| | 5 Oct | Registration deadline for new Self Assessment | | 31 Oct | Paper return deadline for 2024/25 |
December 2025
| Date | Event | |------|-------| | 30 Dec | File online to have tax collected via PAYE (if under £3,000) |
January 2026
| Date | Event | |------|-------| | 31 Jan | Online return deadline for 2024/25 | | 31 Jan | Payment deadline for 2024/25 tax | | 31 Jan | First payment on account for 2025/26 |
July 2026
| Date | Event | |------|-------| | 31 Jul | Second payment on account for 2025/26 |
January 2027
| Date | Event | |------|-------| | 31 Jan | Online return deadline for 2025/26 | | 31 Jan | Payment deadline for 2025/26 tax | | 31 Jan | First payment on account for 2026/27 |
Late Filing Penalties
Missing the 31 January deadline triggers automatic penalties:
| How Late | Penalty | |----------|---------| | 1 day late | £100 | | 3 months late | £10 per day (up to 90 days = £900) | | 6 months late | £300 or 5% of tax due (whichever is higher) | | 12 months late | Additional £300 or 5% of tax due |
Maximum penalty: £1,600 for being 12+ months late, plus potential additional penalties for serious cases.
The £100 Penalty
The initial £100 penalty applies even if you owe no tax. It's a penalty for late filing, not late payment.
Example: You're employed, pay all tax through PAYE, but were briefly self-employed earning £500. You file your return on 2 February (one day late). Penalty: £100—even though you owe nothing.
Late Payment Penalties
Separate from filing penalties, late payment incurs:
| How Late | Penalty | |----------|---------| | 30 days late | 5% of tax unpaid | | 6 months late | Additional 5% of tax unpaid | | 12 months late | Additional 5% of tax unpaid |
Plus interest: HMRC charges interest on late payments from the due date.
Combined Impact
If you file late AND pay late, you face both penalties:
Example: File 3 months late, pay 6 months late on £5,000 tax.
- Filing: £100 + £900 (90 days × £10) = £1,000
- Payment: £250 (5%) + £250 (5%) = £500
- Plus interest
- Total penalties: ~£1,500+
Reasonable Excuse
HMRC may cancel penalties if you have a "reasonable excuse":
| May Be Accepted | Unlikely to Be Accepted | |-----------------|------------------------| | Serious illness | Being busy | | Death of close family member | Not knowing the deadline | | HMRC system failure | Relying on someone else | | Fire, flood, theft of records | Lack of funds to pay | | Unexpected hospital stay | Finding it difficult |
If you have a reasonable excuse, contact HMRC as soon as possible.
How to Avoid Missing Deadlines
1. File Early
Don't wait until January. Once the tax year ends (5 April), you can file immediately.
| File In | Benefit | |---------|---------| | April–June | Maximum time to find errors | | July–September | Plenty of time if issues arise | | October–December | Still comfortable | | January | Risky—problems could make you late |
2. Set Calendar Reminders
| Reminder | When | |----------|------| | Start preparing return | 1 November | | Aim to file by | 15 January | | Final deadline | 31 January | | Payment deadline | 31 January | | Second payment on account | 31 July |
3. Use Tax Software
Software with deadline reminders helps you stay on track:
- Automatic notifications before deadlines
- Progress tracking throughout the year
- One-click filing when ready
4. Gather Records Throughout the Year
Don't scramble in January. Keep records organised:
- Monthly bank reconciliation
- Expense receipts stored digitally
- Income logged as received
Weekend and Bank Holiday Deadlines
If a deadline falls on a weekend or bank holiday, the deadline is usually the next working day.
| Deadline Date | Falls On | Actual Deadline | |---------------|----------|-----------------| | 31 January 2026 | Saturday | Monday 2 February 2026 | | 31 July 2026 | Friday | Friday 31 July 2026 |
However: Don't rely on this. File and pay before the stated date to avoid risk.
Making Tax Digital Changes
From April 2026 (income over £50,000) or April 2027 (over £30,000), Making Tax Digital adds quarterly deadlines:
| Quarter | Period | Deadline | |---------|--------|----------| | Q1 | 6 Apr – 5 Jul | 7 August | | Q2 | 6 Jul – 5 Oct | 7 November | | Q3 | 6 Oct – 5 Jan | 7 February | | Q4 | 6 Jan – 5 Apr | 7 May | | Final declaration | Full year | 31 January |
The 31 January deadline remains for the final declaration.
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- Deadline reminders — notifications before key dates
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Summary: Key Dates at a Glance
| Deadline | Date | For | |----------|------|-----| | Registration | 5 October | New Self Assessment users | | Paper return | 31 October | Those filing on paper | | PAYE collection request | 30 December | Have tax collected via wages | | Online return | 31 January | Most filers | | Tax payment | 31 January | Tax owed for the year | | First payment on account | 31 January | Advance payment for next year | | Second payment on account | 31 July | Advance payment for next year |
Remember: File early, pay on time, avoid penalties.