Self Assessment deadlines, and why your January bill can be bigger than you expect
The 31 January bill often surprises people in their second year of self-employment. Payments on account are the reason. A clear guide to the dates and the sums.
If you are self-employed, a landlord, or have income that is not taxed at source, you probably need to file a Self Assessment tax return. If you are new to it, you must tell HMRC by 5 October after the end of the tax year.
The 2025/26 tax year
- 5 Oct 2026Register for Self Assessment, if you have not filed before
- 31 Oct 2026Paper tax returns due
- 31 Jan 2027Online tax return and balancing payment due, plus first payment on account for 2026/27
- 31 Jul 2027Second payment on account for 2026/27
How payments on account work
Payments on account are advance payments towards next year’s bill, each half of the previous year’s tax. You do not have to make them if last year’s bill was under £1,000, or if more than 80% of your tax was collected at source, for example through a tax code.
In HMRC’s own example, a bill of £3,000 for one year, with £1,800 already paid on account, leaves a balancing payment of £1,200 in January, plus the first payment on account of £1,500 towards the next year: £2,700 due on one day.
If your income has fallen
You can ask HMRC to reduce your payments on account if you expect this year’s bill to be lower. Be realistic: if you reduce them too far, you pay interest on the difference.
Budget 2026 announced that, from April 2029, Self Assessment taxpayers who make payments on account will pay more regularly during the year. The details are still to come.
This insight is general information, not advice for your circumstances. Talk to us before acting on it.