HMRC letters • Plain English

Self Assessment late filing penalty notice

HMRC charges an automatic penalty when a Self Assessment return is filed late, even if you owe no tax. The first penalty is £100. If you still have not filed, more penalties follow, so the notice is a prompt to file now.

By The HandySums teamLast checked:

Who gets this

Sole traders, subbies and landlords who missed a return deadline.

How to recognise it

  • It says "penalty" and names a tax year, for example 2025 to 2026.
  • It shows an amount (£100 for the first one) and the date of the notice.
  • Later notices cover daily penalties after 3 months, then a 5% or £300 penalty at 6 months and again at 12 months.
  • It comes in your HMRC online account or by post, not from an email asking you to click a link to pay.

What to do

  1. Check you really needed to file. If you have stopped being self-employed or never needed a return, tell HMRC through the online service straight away.
  2. If you do need to file, file the return as soon as you can. Every month you wait adds more.
  3. Pay the penalty within 30 days of the date on the notice, using the reference on the notice.
  4. If you had a reasonable excuse (for example serious illness), you can appeal against the penalty.

By when

Pay a penalty within 30 days of the date on the penalty notice. File the return as soon as possible.

What happens if you ignore it

  • £10 a day for up to 90 days after 3 months (maximum £900).
  • A further 5% of the tax due, or £300 if that is more, at 6 months, and again at 12 months.
  • Separate late payment penalties of 5% of the unpaid tax at 30 days, 6 months and 12 months, plus interest.

Official GOV.UK pages

Not sure it is genuine?

Do not use any link or phone number printed in a message you are unsure about. Check the list of genuine HMRC letters, then find HMRC’s contact details on GOV.UK yourself. You never need to upload your letter to HandySums, and we would never ask.

CalculatorCheck your January and July paymentsYour 31 January and 31 July payments, the balancing payment, and whether CIS means you owe none.GuideSelf Assessment deadlines guideEvery key date for 2025/26 and 2026/27, and exactly what it costs to file or pay late.DatesAll HMRC dates, with a calendar fileEvery HMRC deadline that matters to the self-employed, with a calendar file.

Sources and review

Last checked: 1 November 2026. What this letter is, the deadlines and the penalties described on this page. Written and checked by the HandySums team against the GOV.UK pages below. HandySums is independent and not an accountancy firm — see how we check our sums.

A guide, not tax advice. Results and explanations are a guide and HMRC has the final say. Always follow the dates and instructions on your own letter, and check with HMRC or a qualified accountant if unsure.