Key Self Assessment Deadlines
Missing your self assessment deadlines can result in significant penalties. Here are the dates you need to know.
Important Dates for 2025/26
| Deadline | Date | What |
|---|---|---|
| Registration | 5 October 2026 | Register for self assessment |
| Paper return | 31 October 2026 | Submit paper tax return |
| Online return | 31 January 2027 | Submit online & pay tax |
| 2nd payment on account | 31 July 2027 | Second instalment |
Penalties for Late Filing
- 1 day late: £100 fixed penalty
- 3 months late: £10 per day (up to 90 days = £900)
- 6 months late: 5% of tax due or £300 (whichever is greater)
- 12 months late: Further 5% or £300
Warning: These penalties apply even if you have no tax to pay or have already paid your tax bill.
Tips for On-Time Filing
- Set calendar reminders for key dates
- Gather records throughout the year
- Use HMRC's online service for faster processing
- Consider using an accountant for complex returns
- File early to identify any tax owed and plan payments