What happens if I miss the 31 January deadline?

HMRC will issue an automatic £100 penalty for a late self assessment tax return, even if you do not owe tax. Interest applies to late payment until you clear the balance. Penalties can increase the longer you delay, so file as soon as possible and pay what you can.

Can HMRC collect my tax bill through PAYE coding?

Yes, but only if you filed by 30 December and met HMRC criteria. After that date, PAYE coding for the current return is not available. If you missed it, pay by 31 January or consider a Time to Pay plan. Filing first is required before setting up an instalment plan.

Who must file a self assessment tax return?

You usually need to file if you are self-employed, a landlord, a partner in a partnership, or received untaxed income. Some investors must report dividends, interest, or capital gains. You may also need to file if your income or benefits changed. Use HMRC’s checker if unsure.

How should I prepare for Making Tax Digital for Income Tax?

Move to digital bookkeeping in 2025. Choose compatible software, keep digital records for income and expenses, and reconcile bank feeds monthly. Run test quarterly summaries to find gaps. A clean, timely self assessment tax return this year gives you accurate opening data for 2026 updates.

Global Market Insights

December 30: HMRC warns £100 fines as Self Assessment deadline nears

ByHuzaifa Zahoor December 30, 2025December 30, 2025

The self assessment tax return deadline is close, and HMRC has warned of automatic £100 fines if you miss 31 January. HMRC reported 4,606 Christmas Day filings, showing many are getting ahead. If you wanted PAYE coding to spread what you owe, that option ended on 30 December. Interest builds on late payments, so filing early helps cut costs and stress. We explain who must file, cash flow moves to consider, and how to prepare for Making Tax Digital from April 2026.