31 January checklist: UK Self Assessment 2025-26

Tax year 6 April 2025 to 5 April 2026. Tick items off as you go.

Key dates

5 October 2026: Last day to tell HMRC you need to file a return for 2025-26, if you have never filed one before.
31 October 2026: Deadline for a paper return.
30 December 2026: Online filing by this date lets HMRC collect a small balance through your tax code, if you qualify.
31 January 2027: Deadline for filing online and for paying what you owe for 2025-26.

Get set up

Check whether you need to file a return (income from abroad, rental income, self-employment and some other income can require one).
If you have never filed: confirm you registered with HMRC (the deadline was 5 October 2026) and that your Government Gateway account works.
Locate your Unique Taxpayer Reference (UTR), a 10-digit number from HMRC.
Keep your National Insurance number to hand.

Gather your paperwork

P60 or P45 and any P11D from each UK employer.
Bank and savings interest statements, UK and foreign.
Dividend vouchers or broker statements.
Pension statements, UK and foreign.
Rental income and expenses for UK and French property.
Any foreign tax certificates or French tax notices (avis d'impôt) for income taxed abroad.
Records of gifts to charity and any pension contributions.

If you have French connections

Convert foreign income to pounds using a consistent, documented rate.
Note which foreign tax you have already paid on each item, in case you claim relief.
Check whether the UK-France tax treaty gives the right to tax to one country for each income type.
Work out which supplementary pages you need (SA106 for foreign income; SA109 for residence).

Filing and paying

Aim to file well before 31 January 2027, because the HMRC online service is busy near the deadline.
Work out the amount due, including any payment on account for next year.
Pay by 31 January 2027. Allow time for the payment to reach HMRC: do not leave it to the last day.
Keep a copy of the submitted return and your payment confirmation for at least the period HMRC requires.

This checklist is general information to help you get organised. It is not tax advice, and Clarofisc is not an accountant or lawyer. Check the dates and your own position on GOV.UK or with a qualified adviser.

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