A £100 penalty notice is one of the most common letters HMRC sends. In the year to 31 March 2026, its systems issued 8,128,750 automated penalties, penalty points and default surcharges. By definition, an automated penalty is issued without individual review: the computer applies the rule, prints the letter and moves to the next record.

The interesting number sits further down HMRC's own annual report. When recipients challenged those automated decisions through a statutory review, 48,189 penalties were cancelled in a single year. HMRC states the result from the other direction: only 35% of the reviewed decisions were upheld.

Read that again slowly. Roughly two in three automated penalties that received a second, human look did not survive it.

This article walks through what those figures mean, how the challenge process actually works, and what a sensible response to an automated penalty notice looks like, whether you are a taxpayer holding one or an adviser holding forty.

HMRC's Annual Report and Accounts 2025 to 2026 puts a precise figure on the automation: 8,128,750 automated penalties, penalty points and default surcharges issued in the year. The report does not break the figure down, but the category by its name spans the system's familiar workhorses: Self Assessment late-filing and late-payment penalties, VAT penalty points and the older default surcharge.

The figure fell from 9,070,279 the year before. The table states both figures in a footnote and moves on without explaining the fall, and the prior year's own restated baseline for 2023-24 stood at 8,186,378, so the drop reads as a return to level rather than a trend. Either way, eight million automated decisions is a volume no human review could precede. The design is issue-first: the system acts, and a person examines the decision only when the recipient objects.

An automated penalty is triggered by a data condition. A return not logged by midnight on the deadline, a payment not matched by the due date, a quarterly submission missing from a digital account. The system reads the condition, applies the statute and issues the notice. Whether the taxpayer had a hospital stay, a bereavement, a broken software feed or a perfectly valid paper filing sitting unscanned in a mailroom is information the trigger has no way to see.

The design is issue-first: the system acts, and a person examines the decision only when the recipient objects.

That is what makes the review statistics so instructive. They are the best published measure of how often an automated decision changes once a person examines it, for the minority of decisions anyone asks to have examined.

The same table in the annual report shows 74,738 statutory reviews of automated penalties and default surcharges dealt with in the year. Outcomes: 48,189 cancelled, a small number varied, and the original decision upheld in 35% of cases. Reviews are the second stage of the process; penalties conceded at the initial appeal stage never reach this table, so total cancellations across all stages run higher than 48,189. The cancellation count has climbed across the published series: 35,876 two years ago, 46,266 last year, 48,189 now. The same table carries a second, less quoted trend running the other way: the upheld share has risen from 26% to 33% to 35%, so more people are challenging and more penalties are falling, even as HMRC defends a slowly growing share of the decisions it reviews.

HMRC's narrative alongside the table is candid about the mechanism. Customers are told how to appeal where they have a reasonable excuse, the department has moved the process into the online account, and the digital route "allows HMRC to quickly and efficiently remove those penalties".

Nothing sinister is required to explain why two in three reviewed penalties fall, and it would be a mistake to read the figure as a 65% error rate. Cancellation and error are different things, and the architecture explains both.

The statute behind most automated penalties builds in a safety valve the software cannot operate: reasonable excuse. A serious illness, a bereavement, a fire, a failure of HMRC's own systems at the deadline. These defences exist in law precisely because life intrudes on filing dates, and every one of them requires a human judgement. The machine issues the penalty to everyone the data condition catches; the excuse only enters the process when the taxpayer raises it.

A large share of cancellations are this scenario: the return really was late, the statute was applied correctly, and a human then accepted the excuse. That is the system working as designed, with the human step placed after issue instead of before it. The design choice is legitimate; its cost is that the excused and the erroneous both start by receiving the same demand.

A return filed on paper and processed late. A payment allocated to the wrong reference. A registration that should have been closed years ago still generating filing obligations. Each produces a penalty that is wrong on the facts, and each is invisible until a person compares the notice against reality.

⚠️ Watch: the review only happens on request. HMRC publishes no accuracy sampling of automated penalties after issue, and paying does not extinguish appeal rights within the window, but a penalty paid without question is unlikely ever to be re-examined.

Around two in three reviewed penalties were cancelled or varied. The population is self-selected: people tend to challenge when they have grounds, so an arbitrary recipient does not inherit a 65% probability, and nobody knows how many of the unreviewed millions would have met the same fate. What the data does establish is narrower and still valuable: among the challenges that reached a statutory review, a free process ended the penalty roughly twice as often as it confirmed it. The practical conclusion is to establish your grounds first, then use the process, because with grounds the published odds are good.

Taking Self Assessment as the most common example, the escalation ladder published on gov.uk runs:

Late payment attracts its own percentages on top, plus interest. A £100 letter shrugged off in February can mature into a four-figure debt by the following winter, all of it automated, none of it examined by a person unless the taxpayer speaks up.

One dating note: for taxpayers inside Making Tax Digital for Income Tax, this ladder is being replaced from the year they join by a points-based system, a penalty point per missed submission deadline and a £200 penalty at four points, with HMRC's guidance giving a no-points easement for 2026-27 quarterly updates; late payment moves to its own percentage regime at the same time. The table above continues to govern annual Self Assessment returns outside MTD.

Take a contractor whose 2024-25 return was, in fact, filed on time through commercial software, but whose submission receipt never matched HMRC's record. The £100 notice arrives in February and goes unread in a folder. From early May the daily penalties run at £10 a day, and by the end of July they have reached their £900 ceiling. At the start of August the six-month charge, the greater of £300 or 5% of the tax due, lands on top of the £1,000 already standing. A five-minute factual check in February, receipt against record, would have ended the matter at £0 through a free online appeal. The same check in September still works, but it now has to unwind three separate charges and explain the delay.

📌 Key window: you normally have 30 days from the date on the penalty notice to appeal. Later appeals need a reason for the delay. The clock runs from issue, not from the day the letter surfaces in a pile.

Before drafting any appeal, answer the factual question. Was the return actually late? Was the payment matched? Was there an obligation to file at all? Where no filing obligation existed, the stronger route is asking HMRC to withdraw the notice to file altogether, which removes the penalties with it rather than excusing them. A surprising share of cancelled penalties fall at this first hurdle, and answering it takes a document trail, not a feeling. This is research in the plainest sense, and doing it against the actual rules matters more than doing it fast. An AI tax research tool that cites the governing legislation and guidance gives you the checkable version of that answer; a generic chatbot gives you a confident paragraph either way.

If the penalty is validly issued, the question becomes reasonable excuse. Gov.uk lists the recognised territory: serious illness, bereavement, software failure, HMRC system problems, postal delays you could not predict. The excuse must have existed at the deadline and the failure must be put right without unreasonable delay once it passes.

For most automated penalties the appeal now runs through the online account, the same digital process the annual report credits for the efficient removal of wrong penalties. The statutory review that follows is a fresh look by an officer outside the original decision chain. Two in three such looks ended the penalty last year.

A review that upholds the penalty can go onward to the First-tier Tribunal, normally within 30 days of the review conclusion. That is a different forum with different economics, and by that stage the quality of the underlying research decides the outcome. The claim you assert needs the source behind it, which is the same discipline our sources and update policy applies to every answer the product gives.

For a practice, the 2025-26 figures reframe penalty triage from an administrative chore into a measurable client service.

Penalty notices cluster around filing seasons. A practice that logs each notice, runs the two factual checks and files appeals inside the window converts a £100-per-letter irritation into demonstrated value. The alternative, advising clients to pay and move on, now has a published counterfactual: two thirds of the reviewed decisions did not stand.

There is a structural lesson here that goes beyond penalties. HMRC deployed automation at scale and pushed the verification burden onto the recipient. The same pattern arrives inside firms as AI enters research and drafting: output produced at volume, with the outcome resting on whoever checks it, and on whether checking is anyone's actual job. The difference is that a firm gets to choose its checking layer. We publish our accuracy benchmark precisely so that the checking layer is measurable rather than assumed, and our guide to choosing AI tax research software sets out the questions that separate verifiable tools from confident ones.

The state's architecture shows what automation at scale looks like when the check is optional and pushed onto the recipient: outcomes turn on whether anyone asks. A professional firm gets to make its checking layer mandatory instead, and that single design choice is most of the difference.

The 2025-26 annual report documents, in its own tables, both halves of a truth the profession suspected. Automated penalties go out in the millions, and when a challenged penalty finally gets a second look, the odds have favoured the taxpayer. The 30-day window, the reasonable-excuse ground and the online appeal route are the machinery for acting on that truth; the research to establish whether a penalty is right is the step that makes the machinery work.

If penalty triage, deadline questions and reasonable-excuse boundaries are part of your daily work, create a GAIN Tax account and put a cited answer behind every appeal you file. More explainers live on the GAIN Tax blog.

How many penalties did HMRC issue automatically in 2025-26? 8,128,750 automated penalties, penalty points and default surcharges, per Table 11 of HMRC's Annual Report and Accounts 2025-26. The previous year's figure was 9,070,279.

What share of appealed penalties get cancelled? Of the statutory reviews of automated penalties dealt with in 2025-26, 48,189 ended in cancellation and HMRC upheld its original decision in 35% of cases. Around two in three reviewed penalties were cancelled or changed. Cancellation covers both penalties wrong on the facts and valid penalties excused for reasonable excuse, and reviewers are a self-selected group who mostly had grounds.

How long do I have to appeal an HMRC penalty? Normally 30 days from the date the penalty was issued. Appeals after that need a reason for the delay. The route for most automated penalties runs through your HMRC online account.

What counts as a reasonable excuse? Recognised examples on gov.uk include serious illness, bereavement, unforeseeable postal delays, software failure and problems with HMRC's own services. The excuse must exist at the deadline, and the failure must be corrected without unreasonable delay once it ends.

Does HMRC check automated penalties before sending them? No. The system issues the notice when a data condition is met. A person examines the decision only if the recipient challenges it, which is why the review statistics measure something narrower than an error rate: how often a challenged decision changes on a second look.

Is the £100 late-filing penalty worth appealing? If the return was on time, the obligation did not exist or a reasonable excuse applies, yes: the appeal is free and an unchallenged penalty can escalate at 3, 6 and 12 months. The £100 does not depend on tax being owed, so a penalty on a nil or refund position is still real money, and where there was no obligation to file, asking HMRC to withdraw the notice to file is the cleaner remedy.