Self Assessment Deadline 2026: Key Dates, Penalties & Tips
The self assessment deadline for the 2025/26 tax year is 31 January 2027 for online filing. If you file a paper return, the deadline is 31 October 2026. Missing these dates can result in automatic penalties starting at £100.
Who Needs to File a Self Assessment?
You must file a self assessment tax return if any of the following apply:
- You were self-employed and earned more than £1,000
- You were a company director (unless it was a non-profit with no pay or benefits)
- You earned rental income from property
- You had untaxed income over £2,500 (e.g. tips, commission)
- You had savings or investment income over £10,000
- You earned over £150,000 in the tax year
- You need to pay the High Income Child Benefit Charge
- You had capital gains that need reporting
Key Dates for 2025/26 Tax Year
| Date | What Happens |
|---|---|
| 6 April 2025 | Tax year starts |
| 5 April 2026 | Tax year ends |
| 31 October 2026 | Paper return deadline |
| 30 December 2026 | Deadline if you want HMRC to collect tax through your PAYE code |
| 31 January 2027 | Online filing deadline + payment deadline |
Penalties for Late Filing
HMRC takes late filing seriously. Here's what you could face:
- 1 day late: Automatic £100 penalty (even if you owe no tax)
- 3 months late: £10 per day, up to £900
- 6 months late: 5% of tax owed or £300, whichever is higher
- 12 months late: Further 5% of tax owed or £300, whichever is higher
In serious cases, HMRC can charge up to 100% of the tax owed as a penalty.
5 Tips to File on Time
1. Register Early
If this is your first self assessment, you need to register with HMRC by 5 October 2026. Registration can take up to 20 working days as HMRC posts your UTR (Unique Taxpayer Reference) by mail.
2. Keep Records Throughout the Year
Don't wait until January to gather receipts. Use cloud accounting software to track income and expenses as you go. This makes filing significantly faster.
3. Understand Your Allowable Expenses
Self-employed individuals can deduct business expenses to reduce their tax bill. Common deductions include office costs, travel, professional subscriptions, and a proportion of home working costs.
4. Set Aside Money for Tax
A good rule of thumb is to set aside 25-30% of your income for tax. Open a separate savings account and transfer money regularly so you're not caught short in January.
5. Get Professional Help
A qualified accountant can ensure you claim all available deductions, avoid common mistakes, and file accurately. At Liberate Accountants, our self assessment service starts from just £300 — and we handle everything from start to finish.
Frequently Asked Questions
How much does it cost to get an accountant to do my self assessment? Professional self assessment services typically range from £150 to £500+ depending on complexity. At Liberate Accountants, our fixed fee starts from £300 with no hidden charges.
Can I file my self assessment after the deadline? Yes, but you'll face penalties. File as soon as possible to minimise charges. HMRC may waive penalties if you have a reasonable excuse.
Do I need to file a self assessment if I'm employed? Most employed people don't need to. However, if you earn over £150,000, have significant untaxed income, or are a company director, you will need to file.
Need help with your self assessment? Contact Liberate Accountants for a free consultation, or learn more about our self assessment service.
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