Tax · United Kingdom
Late tax return: Notice of penalty assessment (SA326D) — the automatic £100 penalty
The SA326D is the automatic penalty notice HMRC issues when a Self Assessment return was not filed by the deadline. The first notice charges a fixed £100 — even if no tax was owed — and can be paid or appealed within 30 days.
How serious: needs actionAlso called: SA326D, £100 late filing penalty, Self Assessment penalty notice
The SA326D is issued automatically when a Self Assessment tax return was not filed by the deadline. The first notice charges the fixed £100 penalty. It is charged even if you owed no tax or were due a refund.
The penalty is only the first rung. If the return stays outstanding, later notices add daily penalties after 3 months and percentage penalties at 6 and 12 months. Filing the return is what stops the ladder.
The notice carries two 30-day windows: one to pay the penalty and one to dispute it. Both run from the date on the notice.
Who sends it
HM Revenue and Customs (HMRC), the UK's tax authority.
An HMRC letter headed 'Late tax return: Notice of penalty assessment' with the reference SA326D at the top of the front page. It states a £100 penalty for the named tax year and warns of daily penalties: 'If your tax return is more than three months late we will charge you a penalty of £10 for each day it remains outstanding.'
The deadline
'You must pay the penalty within 30 days of the date on the penalty notice.' To dispute: 'You usually have 30 days from the date your penalty was issued to contact HMRC or make an appeal.'
'You must pay the penalty within 30 days of the date on the penalty notice.' To dispute it: 'You usually have 30 days from the date your penalty was issued to contact HMRC or make an appeal.' Both periods run from the date on the penalty notice.
If you do nothing
The £100 penalty stands and the ladder keeps climbing while the return is unfiled: £10 a day after 3 months (maximum £900), 5% of the tax due or £300 (whichever is greater) at 6 months and again at 12 months, plus 5% late-payment penalties on unpaid tax at 30 days, 6 months and 12 months, and interest on everything owed. Unpaid penalties are collected like any other HMRC debt.
How it escalates
- 01The penalty remains due and interest is charged if it is paid late — 'You'll be charged interest if you pay after the deadline'.
- 02Return still outstanding at 3 months: £10 daily penalties, up to £900.
- 03At 6 months and 12 months: further penalties of 5% of the tax due or £300, whichever is greater, each time.
- 04The debt (penalties plus any tax) enters HMRC's enforcement process: debt collection agencies, taking control of goods, direct recovery from bank accounts, court action.
Common questions
I owed no tax. Why am I being charged?
The £100 penalty is for filing late, not for owing tax. It applies even when no tax was due or a refund was owed.
How long do I have?
30 days from the date on the notice, both to pay and to appeal.
Does the penalty grow?
Yes, while the return stays unfiled: £10 a day after 3 months up to £900, then 5% of the tax due or £300 at 6 and 12 months, plus interest.
How is an appeal made?
Online, or by post on form SA370, within 30 days, giving details of a reasonable excuse.
Sources
Facts verified against the sources below on 28 August 2026.
- Self Assessment tax returns: Penalties — GOV.UKofficial
- Pay a Self Assessment penalty — GOV.UKofficial
- Disagree with a tax decision or penalty: Appeal against a penalty — GOV.UKofficial
- Check when to appeal a Self Assessment penalty for late filing or late payment — GOV.UKofficial
- Self Assessment: Appeal against penalties for late filing and late payment (SA370) — GOV.UKofficial