Self-Assessment Tax Return Deadlines UK 2025/26

Key Deadlines

• 5 October 2026 — Register for self-assessment if you are new
• 31 October 2026 — Paper tax return deadline
• 31 January 2027 — Online tax return deadline + pay tax owed
• 31 July 2027 — Second payment on account due

Who Needs to File?

You must file a self-assessment tax return if you are: self-employed with income over £1,000, a company director, earning over £150,000, have untaxed income (rental, investments, foreign), need to claim tax relief on expenses over £2,500, or receive child benefit and earn over £60,000.

Penalties for Late Filing

• 1 day late: £100 fine
• 3 months late: £10/day (up to £900)
• 6 months late: additional £300 or 5% of tax owed
• 12 months late: additional £300 or 5% of tax owed

Estimate your tax bill with our Self-Assessment Calculator.