Self Assessment Deadlines 2026/27
The deadlines that actually matter
For any given tax year (running 6 April to 5 April), you have two main filing options: a paper return, due by 31 October following the end of the tax year, or an online return, due by 31 January — three months later. Almost everyone files online given the later deadline and faster processing. Your balancing payment for the tax year is also due by that same 31 January.
Payments on account
- If your last tax bill was over £1,000 and less than 80% of your tax was collected at source (e.g. via PAYE), HMRC usually requires two advance "payments on account" toward next year’s bill
- These fall due on 31 January and 31 July, each set at 50% of your previous year’s tax bill, with any difference settled (or refunded) once your actual return is filed
- If you know your income will be lower this year, you can apply to reduce your payments on account — but reducing them too far triggers interest if your final bill turns out higher than expected
What late filing and late payment actually cost
Missing the 31 January online filing deadline triggers an immediate £100 penalty, even if you owe no tax. After 3 months, daily penalties of £10 accrue for up to 90 days (up to £900 more). At 6 and 12 months late, HMRC adds a further penalty of the greater of £300 or 5% of the tax due, at each stage. Late payment carries daily interest from the due date, plus separate penalties of 5% of the unpaid tax at 30 days, 6 months and 12 months late — on top of, not instead of, the filing penalties.