Self Assessment Deadlines 2026/27
Missing Self Assessment deadlines triggers automatic penalties. Here's everything you need to know about the key dates and what happens if you're late.
Key Deadlines for 2025/26 Tax Year
| Deadline | Date | What's Due |
|---|---|---|
| Tax year ends | 5 April 2026 | End of 2025/26 |
| Register for Self Assessment | 5 October 2026 | If new to SA |
| Paper return deadline | 31 October 2026 | Paper filing |
| Online return deadline | 31 January 2027 | Online filing |
| Payment deadline | 31 January 2027 | Tax owed |
| 2nd payment on account | 31 July 2027 | If applicable |
Penalties for Late Filing
| How Late | Penalty |
|---|---|
| 1 day late | £100 |
| 3 months late | £10/day (max 90 days = £900) |
| 6 months late | £300 or 5% of tax (whichever higher) |
| 12 months late | £300 or 5% of tax (whichever higher) |
Maximum late filing penalty: £1,600 plus interest on late tax.
Penalties for Late Payment
| How Late | Penalty |
|---|---|
| 30 days late | 5% of tax owed |
| 6 months late | Additional 5% |
| 12 months late | Additional 5% |
Total late payment penalty: Up to 15% plus daily interest.
Who Needs to File?
You must file Self Assessment if you:
- Are self-employed with income over £1,000
- Earned over £100,000
- Received rental income over £10,000
- Need to claim tax relief (pension contributions, Gift Aid)
- Have High Income Child Benefit Charge liability
- Are a company director
- Have foreign income
- Received untaxed income (dividends over £500, etc.)
How to File
- Register (if new) by 5 October
- Gather records: P60, P45, bank statements, expenses
- Log in to HMRC online account
- Complete the relevant sections
- Submit by 31 January
- Pay any tax owed by 31 January
Related Calculators
- Self-Employed Tax Calculator - Calculate your tax
- Income Tax Calculator - Full tax breakdown