What is the last date to file income tax return for 2025/26?

The deadline to file your 2025/26 Self Assessment tax return online is 31 January 2027. Miss it, and HMRC immediately begins charging penalties and interest.

For the 2025/26 UK tax year (6 April 2025 to 5 April 2026), the key filing deadline is 31 January 2027 for online returns. If you file on paper, the deadline is 31 October 2026.

Key Deadlines for the 2025/26 Tax Year

• 31 October 2026 – Paper Self Assessment return filed
• 31 January 2027 – Online Self Assessment return filed AND any balancing payment due
• 31 January 2026 – First payment on account for 2025/26 tax year
• 31 July 2026 – Second payment on account for 2025/26 tax year
• 5 October 2026 – Deadline to register for Self Assessment if you have new income

Payment on Account Explained

If you owe more than GBP 1,000 in tax for 2025/26, HMRC requires you to make payments on account – advance instalments towards your next tax bill. Each payment is 50% of your previous year tax liability. The first is due 31 January 2027 and the second is due 31 July 2027.

Penalties for Late Filing

Missing the 31 January 2027 deadline triggers an automatic GBP 100 penalty. Further penalties stack up: 2 months late = additional GBP 100; 6 months late = 5% of tax due or GBP 300; 12 months late = another 5% of tax due or GBP 300.

Interest on Late Payment

Any tax owed accrues HMRC Daily Interest (currently 7.25% per annum – 4.25% above Bank of England base rate) from the due date until paid. Interest compounds daily and is charged on top of any penalties.

What If You Cannot Pay by 31 January?

HMRC has practical options: Time to Pay arrangement (installment plan via Personal Tax Account or 0300 200 3822), payment by debit card or Direct Debit online. Even delay does not eliminate the debt – interest accumulates and enforcement powers can eventually be used.

Practical Checklist Before 31 January 2027

• Gather all income records: P45/P60, self-employment invoices, property income, bank interest, dividends
• Claim all allowable expenses: professional subscriptions, office costs, travel, EIS/VCT relief
• Check your tax code if employed – errors cause unexpected bills later
• Register for VAT if self-employed turnover exceeds GBP 90,000
• Consider voluntary National Insurance contributions to fill gaps near state pension qualifying years

How to File Online

Self Assessment is filed through HMRC online portal at www.gov.uk/self-assessment-tax-returns. You need a Government Gateway account. The system saves partially completed returns. If your affairs are complex, consider using HMRC-compatible software or a tax adviser.