Self Assessment Cheat Sheet 2025/26

1. Do I need to file a return?

You will usually need to file a Self Assessment tax return for 2025/26 if any of these apply.

• Self employed

  Gross income over £1,000 (turnover, not profit).

• Rental income

  Over £10,000 gross, or over £2,500 profit. Over £1,000? Tell HMRC.

• Other untaxed income

  Tips, commission or casual work over £2,500.

• Savings or dividends

  £10,000 or more. Dividends over £500? Tell HMRC.

• Capital gains

  Tax to pay above the £3,000 annual exemption.

• Child Benefit

  Either of you claims it and you or your partner earn over £60,000 individually.

• Partners

  Any partner in a business partnership.

• HMRC letter

  Sent a notice to file? You must file, even if you owe nothing.

2. Key dates

1. 5 Oct 2026 Register Passed

   New to Self Assessment?

   Deadline to register with HMRC. Missed it? Register now.

2. 31 Oct 2026 Paper Passed

   Paper returns due

   Only if you are still filing on paper.

3. 30 Dec 2026 Online

   Pay through your wages

   Employed and owe under £3,000? File online by now and HMRC can collect it via your tax code.

4. 31 Jan 2027 The big one

   Online return + balancing payment + 1st payment on account

   Three deadlines on one day.

5. 31 Jul 2027 Payment

   2nd payment on account due

   The second half of your advance payment for 2026/27.

3. Late filing penalties

• 1 day late £100
• 3 months late £10 a day (up to £900)
• 6 months late £300 (or 5% of tax)
• 12 months late £300 (or 5% of tax)

The £100 applies even if you owe nothing. Paying late adds 5% at 30 days, 6 and 12 months, plus interest.