UK Tax Deadlines 2025: Self Assessment and HMRC Key Dates
Missing a UK tax deadline triggers automatic HMRC penalties, even if you owe no tax. For expats, non-residents, and those with UK rental income or foreign income, understanding the full UK tax calendar is essential. This guide covers every key date for the 2024/25 and 2025/26 UK tax years.
5 October 2025, register for Self Assessment
If you need to file a Self Assessment return for 2024/25 and you've never registered before (or you de-registered in a previous year), you must notify HMRC by 5 October 2025. Registration is done through HMRC's online services or by completing form SA1. Once registered, HMRC will send you a Unique Taxpayer Reference (UTR), allow up to 10 working days for this to arrive. Without a UTR, you cannot file online.
31 October 2025, paper return deadline
If you choose to file a paper Self Assessment return for 2024/25, it must reach HMRC by 31 October 2025. Paper filing is less common but may be necessary if you need supplementary pages that HMRC's online service doesn't support (such as SA109 for non-residents). Using commercial software, as we do, allows electronic filing even with supplementary pages.
31 January 2026, online return and payment deadline
The key deadline: your 2024/25 Self Assessment return (filed online) must be submitted, and any tax owed must be paid, by 31 January 2026. This date also includes the first payment on account for 2025/26, typically 50% of your 2024/25 tax bill. Many people are caught off guard paying 150% of expected at this deadline (one year's bill plus a payment on account). Late payment charges: 5% surcharge after 30 days, further 5% after 6 months, another 5% after 12 months.
31 July 2026, second payment on account
The second payment on account for 2025/26 (the other 50% of your 2024/25 bill) is due 31 July 2026. If your actual 2025/26 tax turns out to be lower than expected, you can apply to reduce your payments on account, but this must be done before the payment date. Under-reducing results in interest charges; over-reducing is fine and the difference is settled in the January balancing payment.
Interest and surcharge rates
HMRC charges interest on late tax payments at the Bank of England base rate plus 2.5%. As of 2025, this is approximately 7.5% per annum. Late filing penalties (for the return itself) are separate from late payment charges: £100 immediately; £10/day from 3 months; £300 or 5% of tax from 6 months; £300 or 5% again from 12 months. HMRC may reduce penalties for a reasonable excuse, but this is harder to establish than many people expect.
Our licensed CPAs and qualified accountants handle your filing from start to finish, applying all relevant exclusions, credits, and treaties.
See pricing →[INSERT: customer testimonial, e.g. "UK freelancer in Edinburgh, Scotland, saved money and stress using Nomadic.Tax"]
- UK freelancer, Edinburgh, Scotland
Frequently asked questions about UK Tax Deadlines 2025: Self Assessment and HMRC Key Dates
What is the UK Self Assessment deadline for 2025?
For the 2024/25 tax year (ending 5 April 2025), the online Self Assessment return and any payment are due 31 January 2026. The paper return deadline was 31 October 2025.
When do I need to register for Self Assessment?
By 5 October after the end of the tax year in which you first need to file. If you needed to file for 2024/25 (ending 5 April 2025), the registration deadline is 5 October 2025.
I filed late, what penalty will I face?
An automatic £100 penalty applies immediately if your return is not filed by the deadline, even if no tax is owed. Further penalties accrue at £10/day from 3 months late, then a further £300 or 5% of tax at 6 and 12 months. The sooner you file, the lower your total penalty.
Can HMRC waive the penalty if I have a good reason?
HMRC may reduce or cancel penalties for a 'reasonable excuse', illness, bereavement, or certain technical failures. Simply not knowing about the deadline is not normally accepted as a reasonable excuse. We can help you draft a reasonable excuse appeal if appropriate.