Who needs to file a self assessment tax return?

You must file if you are self‑employed, a landlord, a company director, or have untaxed income such as dividends, capital gains, or side gigs. HMRC may also require a return if your income or reliefs need checking. If you received a notice to file, you must submit a return even with no tax due.

What happens if I miss the 31 January deadline?

You get a £100 late filing penalty immediately. Further penalties can build after three, six, and twelve months. Late payment also attracts percentage penalties and interest. File as soon as possible to stop extra charges. If you cannot pay in full, set up a Time to Pay plan to spread the cost.

Do I have to pay my tax bill on 31 January too?

Many people must pay both the balancing bill for the last tax year and the first payment on account for the current year on 31 January. A second payment on account is due on 31 July. Check your HMRC calculation to confirm amounts and plan cash flow early.

Can I reduce my payments on account?

Yes, if your current year’s income is likely to be lower, you can ask HMRC to reduce payments on account. Estimate carefully and keep evidence, because underpaying can lead to interest and potential penalties. Update your estimate if circumstances change, and review again before the 31 July instalment.

Global Market Insights

January 07: HMRC Warns 5.65m Still to File Self Assessment or Face Fines

ByHuzaifa Zahoor January 7, 2026January 7, 2026

HMRC warns that 5.65 million people still need to file a self assessment tax return before the 31 January deadline. Missing the cut-off triggers a £100 fine, with more charges if filing or payment is late. For many, the balancing bill and the first payment on account are also due on 31 January, so cash flow matters. We explain what to do now, how penalties work, and practical steps to avoid costly mistakes.