HMRC Estimated Tax Bill: Can You Challenge It?

Yes, you can cancel an HMRC estimated tax bill by filing the tax return HMRC says is missing, as long as you do it within the time limit. You have no right to appeal against the estimate itself, so the return is your way out, and the figures in it replace HMRC’s guess.

People usually ask this after a letter arrives demanding tax they have never worked out. Some did not know they had to file a return. Others thought their accountant had filed it. The surprise is that HMRC can demand and collect the estimate even though it is only a guess, and that the time you have to put it right is shorter than most people expect. Our guide to late Self Assessment returns covers the penalties that usually come with a missed return.

What Is an HMRC Estimated Tax Bill?

An HMRC estimated tax bill is the tax office’s own guess at what you owe. HMRC sends it when a tax return it told you to file has not arrived on time. The legal name is a “determination”. HMRC makes it “to the best of his information and belief” under section 28C of the Taxes Management Act 1970, which means it uses whatever information it already holds about you.

The estimate is not a final bill. HMRC’s own manual says it is “treated as a self assessment until such time as the taxpayer files the tax return”. In plain words, it stands until your real return replaces it. HMRC’s Self Assessment legal framework on determinations sets out how this works.

Why Has HMRC Sent Me an Estimate?

HMRC can only make an estimate if it gave you a notice to file a return and the return did not arrive by the filing date. For most people the filing date is 31 January after the end of the tax year, so for the 2024-25 tax year it was 31 January 2026. If HMRC sent the notice after 31 October, the date is three months from the day the notice was given. That is the rule in section 28C(6).

The usual reasons are simple. You may not have realised you needed to file after starting to work for yourself or renting out a property. You may have started the return and never sent it. Or someone else may have been meant to file it for you. Selling on sites such as eBay, Vinted or Airbnb can also lead here, because online platforms now report seller earnings to HMRC, as our article on HMRC’s data on almost 4 million online sellers explains. Our tax litigation page sets out the HMRC disputes we act in.

Can I Appeal an HMRC Estimated Tax Bill?

Not against the amount. HMRC’s manual says: “There is no right of appeal against the determination.” The same applies to a company, where HMRC’s guidance says “You can’t appeal against the amount of the determination of how much Corporation Tax you must pay”. You can read that rule in HMRC’s guidance on company determinations.

That sounds harsh, but the estimate can be cancelled by filing the return. Appeals still matter for the other letters that often arrive alongside it, such as penalty notices. Our guide to appealing to HMRC and our guide to First-tier Tax Tribunal appeals explain how those appeals work.

How to Cancel an HMRC Estimate: File the Missing Return

Gather your income and expense records for the year in question, file the missing return, and pay any tax it shows. If your own records are missing, bank statements and invoices usually fill most of the gaps. Once HMRC has a proper return from you, it replaces the estimate. HMRC’s manual says any tax you overpaid against the estimate will be repaid. If your real figure is higher than HMRC’s guess, you pay the higher figure.

Do this quickly, because the estimate can also set your payments on account for the following year, according to the same HMRC manual page. A wrong estimate can therefore distort later bills until it is corrected. If you cannot pay what your return shows, ask about a Time to Pay arrangement. HMRC’s guidance on paying late says you can set up a Self Assessment payment plan online only if you owe £30,000 or less, are within 60 days of the payment deadline and have filed your latest return. That is one more reason to file first. If you are outside those limits, you will need to speak to HMRC directly.

Time Limit to Replace an HMRC Estimate

The law gives you two possible dates. Under section 28C(5), a return that replaces an estimate must be made “before the end of the period of 3 years beginning with the filing date” or “before the end of the period of twelve months beginning with the date of the determination”. HMRC’s debt management manual treats the later of those two dates as your deadline.

Here is an example. Say HMRC sends an estimate in June 2026 for the 2024-25 tax year. The filing date was 31 January 2026, so the three-year point falls at roughly the end of January 2029. That is later than twelve months from June 2026, so on HMRC’s approach you would have until then. Miss it and the estimate stays. HMRC’s manual says the determination “can only be replaced by an actual self assessment made within that time”. Your options after that are narrow and depend on the facts, so speak to us as soon as you see the date has passed. You can start with our case assessment form.

Do I Have to Pay the Estimate While I Sort Out the Return?

HMRC treats the estimate as real tax. Its manual says the tax charged “is payable and enforceable until it is replaced by a self assessment”. The payment date is the date that would have applied if you had filed on time, so interest and collection steps can start before you have done anything. Keep proof of every payment you make, because it helps when HMRC works out the refund. If recovery has already begun when your return arrives, section 28C(4) lets HMRC carry on, but only for the unpaid part of the figure in your return.

Collection can move fast. HMRC has the power to take money directly from a bank account once a debt is established, and our guides on how an HMRC debt becomes enforceable and on HMRC enforcement action show the steps in order. A statutory demand has its own short deadline, and our guide to setting aside a statutory demand explains it.

HMRC Estimate, Discovery Assessment or Penalty: Which Letter Is Yours?

People often mix up three different letters. An estimate arrives when you filed nothing. A discovery assessment arrives when you did file and HMRC now says too little tax was declared, and our guide to HMRC discovery assessments explains how to challenge one. A penalty notice is a separate charge for being late or careless, and our page on HMRC penalties covers the main types.

The difference matters because your rights differ. You cannot appeal an estimate, but you can appeal assessments and penalties. HMRC’s guide to tax appeals says “The deadline is usually 30 days from the date of the letter.” If you have missed that date, read our guidance on late appeals against HMRC and on late appeals to the Tax Tribunal.

Late Filing Penalties and Interest on Top of the Estimate

The estimate does not replace late filing penalties. They run separately and can arise even when no tax turns out to be due. HMRC’s current figures are £100 for a late return, then £10 a day after three months up to £900, then 5% of the tax due or £300, whichever is greater, at six months and again at twelve months. Late payment adds 5% of the unpaid tax at 30 days, six months and twelve months, and interest runs as well. HMRC’s penalty estimator gives a quick figure, and our guide to late Self Assessment returns, penalties and enforcement explains the timeline.

A penalty can sometimes be challenged by arguing a “reasonable excuse” for the late return, as our notice of appeal guide describes. Interest is charged separately on tax that is paid late. If HMRC rejects your first challenge, our page on what happens after HMRC rejects a review sets out the next steps.

What About an Estimated Tax Bill for a Company?

A company gets the same kind of estimate when it does not file its Company Tax Return. HMRC’s company determination guidance says HMRC normally waits “at least six months after” the filing deadline before issuing one. The full amount is due immediately, and interest runs from the normal due date, usually nine months after the accounting period ends. The company must file the return and pay.

An unpaid company estimate can lead to a statutory demand and then a winding-up petition. Our guides to understanding and responding to statutory demands, whether HMRC can wind up your company and negotiating with HMRC before a winding-up petition cover what directors can do, and our HMRC debts and winding-up petitions FAQs answer common questions.

Did Your Accountant Fail to File Your Return?

If you paid an accountant or agent to file your return and they did not, you may be able to recover the penalties and interest from them. You would have to prove they were at fault and that you lost money as a result. Our pages on negligent accountants and negligent tax advisers explain what a claim involves.

Deal with HMRC first, because the time to replace the estimate is short and a claim can follow. The usual time limit for a claim is six years, though a later start date can apply in some cases, as we explain in our guide to the limitation period for a professional negligence claim, and our page on how compensation is calculated shows what can be recovered.

Deadlines: How Long Do You Have to Act?

Several clocks can run at once. The time to replace the estimate is the later of three years from the filing date or twelve months from the date of the estimate. An appeal against a penalty is usually due within 30 days of the letter. Our page on when HMRC enforcement becomes insolvency action shows how quickly an unpaid company estimate can escalate.

If you get an estimate, take four steps in this order. Check the date on the letter and the tax year it covers. Gather your figures and file the missing return. Pay what the return shows, or ask HMRC about a payment plan. If a time limit has passed, or a penalty looks unfair, speak to us, because late routes exist for some decisions, and our First-tier Tax Tribunal appeals guide explains the process.

How We Can Help with an HMRC Estimated Tax Bill

We act for individuals and companies who face HMRC penalties, assessments and enforcement, and for directors facing statutory demands or winding-up petitions that follow an unpaid HMRC debt. Our HMRC tax dispute lawyers page sets out the work in more detail.

We are dual qualified solicitors and barristers, with chambers in Middle Temple next to the Royal Courts of Justice. We offer a fixed fee advice conference with both a solicitor and a barrister, and you can start with our case assessment form.

This article is general information, not legal advice.