Can You Appeal An HMRC Determination Or Dispute Your Tax Return?

You have a letter from HMRC headed "Determination of tax due", for a tax year you never sent a return for. The figure is far higher than anything you could really owe, and you have found the tribunal's appeal form online.

Stop there. A determination is HMRC's own estimate of your tax, made because no return arrived, and it cannot be appealed at all: an appeal against one is struck out. The remedy lies in your own hands, and its deadline is already running.

HMRC's manuals call it a "Revenue Determination" (form SA323, SAM50030), and GOV.UK has no public guide to it.

The short answers:

• You have a determination. No appeal. File the return and the determination is replaced automatically. Deadline: the later of 3 years from the filing date or 12 months from the date of the determination.
• You filed a return and it is wrong. Amend it within 12 months after the filing date. After that, claim overpayment relief within 4 years after the end of the tax year.
• HMRC changed your figures. Reject a correction within 30 days, or appeal a closure notice or discovery assessment within 30 days.
• Late-filing penalties are separate, and they can be appealed.

An inheritance tax Notice of Determination is a different document with a real appeal right, within 30 days: see our inheritance tax appeals guide.

What Is An HMRC Determination?

Under section 28C TMA 1970, two things must be true: HMRC sent you a notice to file a return under section 8, and you did not deliver it by the filing date (normally 31 January after the tax year, or three months after a notice issued later than 31 October). An officer may then determine your tax "to the best of his information and belief".

With no return, HMRC estimates, and estimates high on purpose: the figure is meant to prompt you to file (SAM50030). Where nothing better is known, its debt manual (DMBM518040) starts from the "previous year's income tax liability plus 20%" where one return is outstanding, then adds "a further 50% each year" as more years go unfiled. These are internal starting points, not law.

The effect is real, though. Until your own self-assessment (the tax calculation in your return) replaces it, section 28C(3) treats the determination "as if it were such a self-assessment" for paying, collecting and charging interest. The amount is enforceable, late-payment interest runs on it at 7.75%, and it sets your payments on account (the advance instalments towards next year's bill). SAM50030 says a claim to reduce payments on account "cannot be made against a determination", but can be made against those it creates for the following year, provided the return for that year is not overdue.

If you do nothing, HMRC collects the determined figure like any other tax debt: debt collection letters, then enforcement such as taking control of goods, county court proceedings or, for larger debts, bankruptcy. Once the replacement window below has closed, the inflated figure is your tax for that year unless special relief succeeds.

Without a notice to file, HMRC has no power to make a determination at all. If you believe you were never validly sent one, raise it with HMRC (see whether the notice to file was validly issued), but filing within the window is still the quickest fix.

Why You Cannot Appeal A Determination

Most HMRC decisions carry a right of appeal, usually within 30 days (see what HMRC letters actually mean). Section 31(1) TMA 1970 lists what can be appealed: HMRC's amendments during an enquiry (a formal check of your return), the conclusions in a closure notice (the letter that ends an enquiry), and "any assessment to tax which is not a self-assessment". A determination is not on the list, and it is not an assessment.

Section 28C(3) names the Parts of the Act on payment, collection and interest (Parts VA, VI, IX and XI) and leaves out Part V, on appeals. The determination counts as your own return for collecting the money and nothing else, and you do not appeal your own return, you replace it.

In Pledger v HMRC [2010] UKFTT 342 (TC), an appellant representing himself put a 2005-06 determination on his notice of appeal. HMRC's officer pointed out that "the Appellant simply needs to file his 2005-06 self-assessment tax return". The tribunal agreed that a determination is not an "assessment", so "no right of appeal against it arises under s 31 TMA". Under rule 8(2)(a) of the tribunal's rules, which requires a strike-out where the tribunal has no jurisdiction, it "accordingly strikes out the appeal insofar as it relates to that issue".

Three consequences follow. There is no postponement of payment under section 55, which needs an appeal to attach to. A Form T240 with a determination on it will go the way of Mr Pledger's. And the tribunal cannot rule that the figure was unfair or that HMRC should have warned you, because it has no power to judge HMRC's fairness.

Meanwhile, you can ask HMRC for time to pay, and HMRC may, at its discretion, informally hold collection while you prepare the return (SAM11020). HMRC's practice is to allow 30 days after a determination for the return to arrive before enforcement, but SAM50030 says that "is not a legislative requirement".

How To Replace A Determination: File Your Return

Filing the return does the job on its own.

The Deadline For Replacing It

Section 28C(5) gives you the later of two periods: 3 years "beginning with the filing date", or 12 months "beginning with the date of the determination". "Beginning with" means the first day counts, so each period ends the day before the anniversary. Count from the dates printed on your own notice, and if you have determinations for several years, each has its own deadline.

Check the determination's own date too. The same first period binds HMRC: a determination must be made within 3 years beginning with the filing date, and HMRC's debt manual says one made outside it is "invalid and illegal to pursue" (DMBM518010). If yours is later than that, write to HMRC and say so.

An illustration: you were sent a notice to file for 2022-23, so the filing date was 31 January 2024, and the determination is dated 1 June 2026. Three years beginning with 31 January 2024 run to 30 January 2027; twelve months beginning with 1 June 2026 run to 31 May 2027. The later date, 31 May 2027, is the deadline. That outlasts the usual time limit for any self-assessment, 4 years after the end of the tax year (section 34A(1); 5 April 2027 here), because section 34A(2)(b) preserves the determination window.

What Changes When Your Return Goes In

HMRC's manual at SALF209 says your self-assessment "automatically replaces the determination without the need for an appeal or arbitration", and that once it does "any tax overpaid will be repaid". Interest and payments on account are recalculated on the true figure (SAM50030). Enforcement already under way continues, but under section 28C(4) only for the tax shown on your return. Replacement works both ways: if your true figure is higher than the determination, you owe the difference.

Penalties work differently. Tax-geared late-filing penalties (those set as a percentage of the tax) calculated on the determination figure must, once you file, be "re-assessed by reference to the amount of tax shown to be due and payable in that return" (paragraph 24 of Schedule 55 FA 2009). Fixed and daily penalties do not move (Self Assessment penalties; daily penalties), but all of them can be appealed under paragraphs 20 and 21 of Schedule 55, including for a reasonable excuse.

File A Real Return, Not A Placeholder

Every return carries the section 8(2) declaration that it is correct and complete to the best of your knowledge, so a nil or guessed return sent in to stop the clock is a false declaration and risks an inaccuracy penalty. If your true position is nil, a nil return is right; SACM12240 expects exactly that from someone who registered for a business that never started.

Get the figures right before you file. The 12 months amendment window runs from the original filing date, not the day you file, so for an old year it has usually closed already; an overstatement may then be correctable only through overpayment relief, if that is still in time. If a figure genuinely cannot be finalised, GOV.UK allows provisional figures, clearly marked as provisional. And a late return can still be enquired into: HMRC has until the quarter day after the first anniversary of the day you file (enquiry time limits).

Check that the return is accepted: Mr Pledger's had been "returned to him for some minor non-compliance", so the determination still stood. For 2020-21 or earlier you need paper forms from the National Archives, posted to Self Assessment, HM Revenue and Customs, BX9 1AS (paper return guide); get proof of posting.

If You Never Needed To File

The usual route where a notice to file should never have been issued is to ask HMRC to withdraw it under section 8B, which lets the late-filing penalties be cancelled too. That door shuts once you have "been served with notice of a determination" (section 8B(3)(b)). After that, the route is a correct return, which may well be nil.

Missed The Deadline? Special Relief

If the replacement window has closed, a return no longer displaces the determination, but the law leaves one door open: "special relief" under paragraph 3A of Schedule 1AB TMA 1970. It is a claim asking HMRC not to collect determined tax you do not owe, or to repay it, and HMRC's guidance at SACM12220 says "there is no time limit for claiming special relief".

A special form of overpayment relief, it gets past three barriers that would block an ordinary claim: the time limit, Case C (another route expired, and before it did you knew, or ought reasonably to have known, that the tax was wrong and that you could use it) and, if you were "neither present nor legally represented during the enforcement proceedings", Case F(a) (tax paid under enforcement). Every other requirement of an ordinary claim still applies.

The Three Conditions

HMRC does not have to give effect to the claim unless all three are met.

Condition A (paragraph 3A(4)): "in the opinion of the Commissioners it would be unconscionable for the Commissioners to seek to recover the amount (or to withhold repayment of it, if it has already been paid)."

Condition B: your affairs with HMRC are otherwise up to date, or arrangements HMRC accepts are in place to bring them up to date.

Condition C: you have not relied on special relief before, whether or not that claim succeeded, unless there are "exceptional circumstances". SACM12260 says HMRC expects this to "normally be strictly applied" and exceptions to be "very rare": a once-only claim.

Condition A is a high bar. SACM12240 calls special relief a "final and exceptional remedy" and defines the key word: "Unconscionable means completely unreasonable or unreasonably excessive." And: "The fact that a determination is higher than the amount which would have been shown on the return ... is not, on its own, sufficient."

HMRC's guidance lists circumstances that may qualify: vulnerability, such as illness or a mental health condition (SACM12245); not receiving HMRC's notices for reasons outside your control; insolvency. It says these will not normally qualify: a business that never started, moving without a forwarding address, ignoring HMRC's letters, plain negligence.

What Your Claim Needs To Show

The claim must be in writing and signed by you personally (SACM12230), explain why collection would be unconscionable and why you did not file in time, and include the actual figures, ideally completed returns (SACM12240). For a health-based claim, SACM12245 looks for letters from a doctor, mental health or social care professional covering the period from the determination to the end of the replacement window. The claim also needs to show that your other years are up to date (Condition B).

HMRC's Enforcement and Insolvency Service decides. If the claim succeeds, interest and surcharges fall, but late-filing penalties stay: fixed penalties are "still payable following a claim for special relief", and daily penalties are "not disturbed by a claim for relief even when the revised tax is reduced to nil" (SACM12270).

If HMRC Says No

Special relief claims are made under Schedule 1A, so if HMRC enquires into yours and issues a closure notice you can appeal within 30 days; a plain refusal or returned claim carries no closure notice, so no appeal. You can complain to HMRC about the handling, then to the Adjudicator's Office. The last resort is judicial review, a court challenge to the lawfulness of the decision, which must be brought promptly and in any event within 3 months (Civil Procedure Rules, rule 54.5(1)). It carries a real risk of paying HMRC's legal costs, and it is not a step to take without advice.

Can You Dispute A Tax Return You Have Already Filed?

Yes. The route depends on who is changing the return.

Amending Your Own Return

Under section 9ZA you can amend your return up to 12 months after the filing date, online or on paper; GOV.UK's corrections page explains both. While that window is open, amendment is the only route: HMRC's guidance at SACM12080 treats overpayment relief as unavailable to anyone who can still amend. If the window has closed and the mistake means you paid too little, GOV.UK says to write to HMRC to report it; telling HMRC before it asks keeps any penalty lower (reducing HMRC penalties).

When HMRC Corrects Your Return

Section 9ZB lets HMRC correct "obvious errors or omissions in the return", and anything else an officer has reason to believe is wrong, within 9 months of the day you delivered it. A correction cannot be appealed, but you can refuse it: section 9ZB(4) says it "is of no effect" if you give notice rejecting it, and the notice must be given within 30 days of the date the correction was issued. If HMRC still disagrees, its next step is an enquiry.

When HMRC Opens An Enquiry

An enquiry ends with a closure notice setting out HMRC's conclusions, which you can appeal within 30 days; see enquiries and closure notices. Under section 9B, an amendment you make while an enquiry is open does not take effect until it closes. If HMRC returns to a year after the enquiry window has shut, it needs a discovery assessment (a new assessment for tax it believes was missed), which also carries a right of appeal.

Overpayment Relief: Reclaiming Tax After The Amendment Window

Once the amendment window has closed, the route is overpayment relief: a written claim under Schedule 1AB to have tax that was not due repaid or cancelled.

The Time Limit Is Strict

Paragraph 3(1) says a claim may not be made more than 4 years after the end of the tax year the return was for.

An illustration: you filed your 2022-23 return by the 31 January 2024 filing date, so the amendment window closed on 31 January 2025. In March 2025 you find £2,400 of allowable expenses you left out. You can claim overpayment relief until 5 April 2027. The expired amendment route could bring Case C (below) into play, but SACM12085 tells officers not to refuse relief "merely because the person could have realised that they should do something about the matter sooner".

Once the time limit has passed, not even a reasonable excuse under section 118(2) helps. In HMRC v Raftopoulou [2018] EWCA Civ 818 the taxpayer, who represented herself at the First-tier Tribunal, had paid about £18,000 for 2006-07. She claimed a repayment on 13 October 2011, about six months after the limit expired on 5 April 2011. On appeal, it was argued for her that a reasonable excuse should extend the limit. The Court of Appeal disagreed: "there is no provision which specifically permits an extension to this period", and "To be valid, a repayment claim must be made within four years of the end of the relevant tax year".

Unlike a late appeal, a late claim cannot be admitted by a tribunal. HMRC has a narrow discretion to accept one (SACM12160), but it is not something to plan around.

When Relief Is Not Given

Paragraph 2 lists eight "Cases" where relief is refused. In plain English:

• Case A: the mistake was in a claim, election or notice, not the return.
• Case B: you still have another route, such as amending or appealing.
• Case C: another route has expired, and before it did you knew, or ought reasonably to have known, that the tax was wrong and that you could use that route. SACM12085 says HMRC carries the burden and "will want to be able to show that the person had behaved recklessly or deliberately".
• Cases D and E: you argued the point on appeal, or knew of it in time to do so.
• Case F: you paid because of HMRC enforcement proceedings, or a settlement of them.
• Cases G and H: the tax was worked out the way it was generally worked out at the time (the "practice generally prevailing").

How To Claim

A claim cannot be made in a return (paragraph 3(4)). It is a letter to HMRC stating clearly that you are claiming overpayment relief, with the tax year, why you overpaid, the amount, whether you have appealed before, and "documentary proof that the tax has been paid" (Schedule 1A, paragraph 2(2)). You must sign the declaration yourself, confirming the claim is correct and complete to the best of your information and belief: GOV.UK says "No one else, including a tax agent, can sign on your behalf."

SACM12150 gives the address as PAYE Self-Assessment, HM Revenue and Customs, BX9 1AS. HMRC works on "process now, check later" (SACM12160): it normally gives effect to a claim first and may enquire into it afterwards. Repayments carry interest, currently 2.75%.

Appealing A Refusal

The only appeal right is against a closure notice ending an enquiry into the claim (Schedule 1A, paragraphs 7 and 9): in writing, within 30 days of its issue, to the officer who issued it. A letter saying the claim is invalid or out of time is not a closure notice; in Raftopoulou the strike-out stood partly because "there was in any event no enquiry into the claim and therefore no appealable closure notice". In HMRC's view (SACM12005), the only challenge to a refusal to accept a late claim is judicial review.

Other Tax Bills You Did Not Calculate Yourself

A Simple Assessment (form PA302) is a bill HMRC calculates for people outside Self Assessment. Under section 31AA you query it within 60 days; once HMRC gives its final response you have 30 days to appeal under section 31A(4A). See our PAYE underpayments guide. A P800 is a calculation, not an assessment, so there is nothing to appeal: contact HMRC to correct it (see our employment income guide).

Companies and VAT-registered businesses have their own versions. A company determination under Schedule 18 FA 1998, paragraphs 36 to 40, is replaced by a return within a similar "whichever is the later" window, with a company special relief in paragraph 51BA (see GOV.UK's company determinations guide and our corporation tax appeals guide). A VAT assessment under section 73(1) VATA 1994 for an unfiled period can be appealed under section 83(1)(p)(i) only "in respect of a period for which the appellant has made a return", so the remedy is again to file it (see best-judgment VAT assessments).

Which Letter Do You Have?

What To Do Now

1. Identify the letter. "Determination of tax due" means no appeal; a closure notice cites section 28A; a discovery assessment cites section 29. Note every date on it.
2. Work out your replacement deadline from the filing date and the date of the determination, and diarise it. If you no longer have the notice, ask HMRC for both dates, and check the determination itself was made in time.
3. File a complete and accurate return; an old year usually cannot be amended afterwards. Keep a copy and proof of posting or the submission receipt.
4. Check it landed. Confirm with HMRC that the return was accepted and the determination has gone.
5. Talk to HMRC about the money meanwhile: ask for time to pay or an informal hold on collection.
6. Appeal any late-filing penalties within 30 days if you have grounds, such as a reasonable excuse; those appeals are separate, and you can ask HMRC for a review or take them to the tribunal.
7. If the window has closed, bring every other year up to date, then send a signed special relief claim with the figures, the reasons and the evidence.
8. For a return you did file, amend within 12 months of the filing date; after that, claim overpayment relief before the 4 years run out, and diarise the 30 days on any closure notice.
9. Get help early. Free advice services may be able to look at a determination or a claim with you; see representation at the tax tribunal.

Key Legislation And Resources

Legislation

• Taxes Management Act 1970, section 8—the notice to file and the declaration; section 8B—withdrawal of a notice to file, barred once a determination is served; section 9—the self-assessment in a return
• Section 9ZA—amending your own return; section 9ZB—HMRC corrections and your right to reject them; section 9B—amendments during an enquiry
• Section 28C—determinations where no return is delivered, their effect and the replacement window
• Section 31—what can be appealed; section 31A—notice of appeal; section 31AA—querying a Simple Assessment
• Section 34A—time limit for making a self-assessment, with the determination carve-out; section 55—postponement of tax pending appeal
• Schedule 1A—claims made outside a return, including proof of payment (paragraph 2) and appeals against closure notices (paragraph 9)
• Schedule 1AB—overpayment relief: the exclusions (paragraph 2), the time limit (paragraph 3) and special relief (paragraph 3A)
• Finance Act 2009, Schedule 55, paragraph 24—re-assessment of tax-geared late-filing penalties when the return is made
• Tribunal Procedure (First-tier Tribunal) (Tax Chamber) Rules 2009, rule 8—striking out where the tribunal has no jurisdiction
• Finance Act 1998, Schedule 18—company determinations (paragraphs 36 to 40) and company special relief (paragraph 51BA)
• Value Added Tax Act 1994, section 73—assessments where no return is made; section 83—the return condition for appealing them
• Civil Procedure Rules, Part 54—judicial review, including the time limit in rule 54.5

HMRC Guidance

• SAM50030—Revenue determinations: purpose, form SA323, effect on interest and payments on account
• SAM10050—items that cannot be appealed
• SAM11020—postponements and informal standover
• SAM121080—time limits for making a self-assessment and replacing a determination
• SALF209—determinations in HMRC's legal framework manual; SALF205—time limits
• DMBM518040—how HMRC calculates the determined amount
• SACM12005—overpayment relief overview and the judicial review line on late claims
• SACM12085—Case C and HMRC's evidential burden
• SACM12150—making an overpayment relief claim: contents, signature and address
• SACM12220—special relief introduction; SACM12240—Condition A and what "unconscionable" means; SACM12260—Condition C; SACM12270—effect on penalties and interest

GOV.UK Guidance

• If you need to change your Self Assessment tax return—amendments and overpayment relief claims
• Sending your Self Assessment tax return—including provisional figures
• How to complete your Self Assessment tax return on paper—paper returns and the postal address
• Simple Assessment—querying a PA302
• If you cannot pay your tax bill on time—Time to Pay
• Complain about HMRC and the Adjudicator's Office

On This Site

• Understanding Your Appeal Rights: What HMRC Letters Actually Mean
• Self-Assessment Penalties: How They're Calculated And How To Challenge Them
• What Is a Reasonable Excuse? (And Will HMRC Accept Yours?)
• HMRC Enquiries and Closure Notices: What To Expect and What To Do
• Discovery Assessments: When HMRC Can Reopen Your Tax And How To Challenge It
• Form T240: How To Fill In Your Tax Tribunal Notice Of Appeal
• Hok v HMRC: Why "It's Not Fair" Is Not A Ground Of Appeal
• Postponing Payment During An Appeal: How Section 55 TMA 1970 Works
• HMRC Says You've Underpaid Tax? How To Challenge A P800, Simple Assessment Or Tax Code
• Interest On Unpaid Tax: How HMRC Calculates It And What You Can Do
• Missed the Deadline? How To Make a Late Appeal to the Tax Tribunal
• What Is The Tax Tribunal? How The First-tier Tribunal (Tax Chamber) Works
• The Complete Timeline of a UK Tax Dispute

This article is for informational purposes only and does not constitute legal or tax advice. For advice specific to your situation, consult a qualified tax adviser, accountant, or solicitor.