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Status at 23 October 2026: current penalty rules apply to the January 2027 deadline
The 2025 to 2026 Self Assessment return and payment are due by 31 January 2027, and the current penalties described here apply to them, even if you started using Making Tax Digital for Income Tax on 6 April 2026. GOV.UK says new points-based penalties apply from the tax year you join Making Tax Digital for Income Tax.
The short version
- HM Revenue and Customs (HMRC) charges a penalty if you file your Self Assessment return or pay late. The first late filing penalty is £100, even if you owe no tax.
- You usually have 30 days from the date on the penalty notice to appeal. If you miss it you must explain why.
- You win if you have a reasonable excuse, or if the penalty was charged wrongly (you filed on time, or did not need to send a return).
- GOV.UK says these will not be accepted: not having enough money, finding HMRC’s online system too difficult, not getting a reminder, and a mistake on your return.
The penalties
| How late | Penalty |
|---|---|
| After the deadline | £100 |
| After 3 months | £10 a day for up to 90 days, at most £900 |
| After 6 months | 5% of the tax due or £300, whichever is greater |
| After 12 months | Another 5% of the tax due or £300, whichever is greater |
The daily penalties only apply if HMRC decides to charge them and sends a notice saying when they start. If 5% of your tax is below £300 each time, the four add up to £1,600 (our arithmetic, not an HMRC figure).
| How late | Penalty |
|---|---|
| 30 days after the due date | 5% of the tax still unpaid |
| 6 months after the due date | A further 5% of the tax still unpaid |
| 12 months after the due date | A further 5% of the tax still unpaid |
You also pay interest on unpaid tax: the Bank of England base rate plus 4%, which was 7.75% from 9 January 2026 on GOV.UK when we checked. A penalty is due within 30 days of the notice, but GOV.UK says that if you appeal you will not have to pay until the appeal is settled. It also says to consider paying: if your appeal fails you pay interest on the penalty from the date it was due, and if it succeeds HMRC repays you with interest.
New points-based penalties replace these from the tax year you join Making Tax Digital for Income Tax (a £200 penalty at 4 points, and 3% or 4% late payment penalties). They do not change earlier years. Your penalty letter tells you how to appeal one.
What counts as a reasonable excuse
HMRC’s Compliance Handbook says a reasonable excuse is something that stopped you meeting an obligation despite you taking reasonable care. The test is objective: what would a reasonable person with your experience and circumstances, who wanted to comply, have done? It has to last until you filed or paid, or you must have acted without unreasonable delay when it ended.
GOV.UK says these may count: a partner or close relative dying shortly before the deadline; an unexpected stay in hospital, or a serious or life-threatening illness; computer or software failure, or problems with HMRC online services; a fire, flood or theft; postal delays you could not have predicted; delays related to a disability or mental illness; being unaware of or misunderstanding your obligation; and relying on someone else who did not file.
GOV.UK says these will not be accepted: a bounced cheque or failed payment for lack of money, finding HMRC’s online system too difficult, not getting a reminder, and a mistake on your return. HMRC’s manual adds that pressure of work and lack of information will not normally count on their own.
The legislation (Finance Act 2009, Schedules 55 and 56) adds three rules. Insufficient funds is not a reasonable excuse unless caused by events outside your control. Relying on another person is not a reasonable excuse unless you took reasonable care to avoid the failure. An excuse that has ended is treated as continuing if you put things right without unreasonable delay.
Agents and accountants. HMRC’s manual says you are responsible for making sure someone you asked to file actually does, and you cannot claim a reasonable excuse merely because they did not. It expects you to have set deadlines and checked progress. It can work where, for example, the agent was ill or bereaved.
How a tribunal looks at it
The First-tier Tribunal uses the approach in Perrin v HMRC (2018), an Upper Tribunal case that HMRC’s manual repeats: what facts do you say amount to a reasonable excuse; which are proven (more likely than not); viewed objectively, do they amount to one, and when did it stop; and did you put it right without unreasonable delay afterwards? HMRC must first prove with evidence that a penalty is due. Your dates answer the last two questions, so get them right.
The 30-day deadline and how to appeal
Appeal within 30 days of the date on the notice. If you miss it, the law says HMRC must agree to a late appeal if you ask in writing, had a reasonable excuse for the delay and asked without unreasonable delay. Otherwise you need the tribunal’s permission.
- Online: start from GOV.UK’s “Appeal a Self Assessment penalty for late filing or late payment” page. You need the date the penalty was issued, the dates you filed and paid, and details of your excuse.
- Form SA370 by post (SA371 for partnerships): send it to Self Assessment, HM Revenue and Customs, BX9 1AS, within 30 days. You tick a reason, such as ill health, bereavement or information technology difficulties, and describe it.
- Letter: GOV.UK says to send a signed letter to the HMRC office for your return, with your name, Unique Taxpayer Reference, and why you were late, with dates.
In your appeal, explain not only what your excuse is but how it stopped you. File your return and pay as soon as you can: the SA370 form says to do so to avoid further penalties.
If HMRC says no
If HMRC does not change its decision you will be offered a review, or you can ask for one at any time after appealing. GOV.UK says reviews usually take 45 days, and the law gives you 30 days from the date of HMRC’s offer to accept. If you disagree with the result you can appeal to the First-tier Tribunal (Tax Chamber), usually within 30 days of the review result letter. GOV.UK says you pay nothing upfront when appealing a penalty, and you can represent yourself.
If there is no reasonable excuse, check the penalty is correct. HMRC can reduce a penalty for special circumstances, but the law says that does not include your ability to pay, so do not count on it.
Our kit
The HMRC Self Assessment Penalty Appeal Pack turns this into a checklist, an evidence checklist, a timeline worksheet, six appeal letters, a review letter and a tracker. It does not send anything to HMRC or guarantee a result.
Frequently asked questions
Can I say I forgot or was too busy?
HMRC’s manual says pressure of work will not normally count on its own. Look for what actually stopped you, and whether it lasted until you filed.
I missed the 30 days. Is it too late?
Not necessarily. You must explain why the appeal is late. Do it straight away.
Sources
Last checked 23 October 2026.
- Penalties, Deadlines and Appeal a Self Assessment penalty, GOV.UK
- Disagree with a penalty, Reasonable excuses, Get a review and Delay payment, GOV.UK
- Appeal to the tax tribunal, GOV.UK
- Penalties for Making Tax Digital for Income Tax, GOV.UK
- HMRC interest rates for late and early payments, GOV.UK
- Compliance Handbook: Reasonable excuse (CH160000), HMRC internal manual
- Finance Act 2009, Schedule 55 and Schedule 56, legislation.gov.uk
- Taxes Management Act 1970, section 49 and section 49C, legislation.gov.uk
Changes to this guide
- 23 October 2026: Published.
This guide is general information written from the official sources listed above and checked on 23 October 2026. It is not legal, tax or financial advice, and Plainfiles is not endorsed by any government body. Rules change, so check the linked official pages for your own situation. Written and designed by Plainfiles with the help of artificial intelligence (AI) tools, then checked against the official legislation and guidance listed in the sources. How we write and check our guides.