Introduction: When HMRC Special Relief Is the Only Door Left
HMRC special relief is the statutory remedy of last resort for a taxpayer whose UK tax bill was estimated by HMRC after a missed return, and who is now too late to replace that estimate with a real return. It exists for one situation, and it is a situation Americans fall into more often than almost anyone else. A US executive leaves London, HMRC keeps writing to the old flat, notices to file go unanswered, and HMRC eventually issues a determination based on the last salary it saw.
Years later, the determination surfaces as a debt. By then, the ordinary routes are closed. You cannot appeal a determination, and the window to displace it with a return has shut. Consequently, the only way to reduce the bill to the tax you actually owed is a claim for HMRC special relief under paragraph 3A of Schedule 1AB to the Taxes Management Act 1970.
This guide explains how that claim works, the three conditions HMRC applies, how the tribunal reviews a refusal, and the US tax consequences that UK-focused guides never mention. TaxYork prepares missed UK tax returns and the matching US returns for Americans on both sides of the Atlantic, so we set out the process in the order it actually unfolds.
How HMRC Special Relief Differs From Overpayment Relief
In short, HMRC special relief is a form of overpayment relief with its own gateway. Ordinary overpayment relief must be claimed within four years of the end of the tax year, and it is barred where you could have used another remedy in time. Special relief removes both obstacles, but only for tax charged by a determination, and only if three extra conditions are met. HMRC's own manual at SACM12220 confirms that, unlike overpayment relief, there is no time limit for claiming it.
Who This Guide Is Written For
Specifically, this guide addresses high-earning Americans and dual national US UK clients who have left Britain with loose ends, investors who stopped filing UK returns after a property or share sale, and company owners whose personal returns slipped while the business took priority. If HMRC has written to you about a determined amount you do not recognise, the sections below apply.
How HMRC Determinations Arise
A determination is HMRC's estimate of your tax when you have been asked to file and have not. Understanding its timetable is essential, because every later option depends on dates.
Notice to File and Section 28C
Under section 28C of the Taxes Management Act 1970, where HMRC has issued a notice to file and no return arrives by the filing date, an officer may determine the income tax and capital gains tax due "to the best of his information and belief". In practice, the estimate is usually built from your last known income, often grossed up. Therefore, a banker who earned £350,000 in his final full London year can receive a determination on a similar figure for a year in which he earned almost nothing in Britain.
The determination then takes effect as if it were your own self-assessment. As a result, HMRC can charge interest on it, add penalties and pursue it through the normal debt collection process, including enforcement.
No Right of Appeal Against a Determination
Crucially, there is no right of appeal against a determination. The only statutory way to remove it is to file the return. Under section 28C(5), the return must be filed before the later of three years from the filing date and twelve months from the date of the determination. HMRC's manual at SACM12245 restates that rule.
For example, the 2021/22 return was due on 31 January 2023. If HMRC issued a determination on 1 August 2025, you could displace it until 31 July 2026, which is twelve months from the determination and later than 31 January 2026. After 31 July 2026, the return no longer displaces anything, and HMRC special relief becomes the only statutory way to reduce the bill.
Why Americans Are Especially Exposed
Americans are exposed for three reasons. First, many leave Britain without telling HMRC, so notices go to an old address. Second, a US-only citizen who is non-resident loses the UK personal allowance, so even a small UK rental income creates a return obligation. Third, many assume that because the IRS already taxes their worldwide income, Britain no longer cares. It does, and missed UK tax returns remain on HMRC's records long after you have moved on.
The Three Conditions for HMRC Special Relief
The statute sets out a gateway and then three conditions. All must be met.
The Gateway: Relief Barred Only by Time or Enforcement
Under paragraph 3A of Schedule 1AB, the claim is available where a section 28C determination exists, you believe the tax is not due, and ordinary overpayment relief would be available except for one of three barriers. Those barriers are the four-year time limit, Case C, where you could have used another remedy in time and knew or ought to have known it, and Case F(a), where HMRC has taken enforcement proceedings. The Case F(a) route is open only if you were neither present nor legally represented during those proceedings.
Condition A: Recovery Would Be Unconscionable
Condition A is that, in HMRC's opinion, it would be unconscionable to recover the determined amount. HMRC's guidance at SACM12240 defines unconscionable as completely unreasonable or unreasonably excessive. Importantly, HMRC states that a gap between the determination and the true liability is not enough on its own. Your claim must also explain why you did not file in time. The manual gives examples of qualifying circumstances, including vulnerability, not receiving HMRC's notices for reasons outside your control, and insolvency.
The same page lists situations where relief will not normally apply. Notably, one of them is a person who moves abroad and fails to respond to HMRC until enforcement begins. That example is aimed squarely at the expatriate profile. Therefore, an American's claim has to show why the notices genuinely did not reach them, rather than simply that they had left.
Condition B: Your Other Affairs Are Up to Date
Condition B requires your affairs with HMRC to be otherwise up to date, or arrangements agreed to bring them up to date. According to SACM12250, this covers every tax HMRC collects, including any partnership you belong to and any company you controlled. Outstanding returns, unanswered information requests and unpaid penalties all count. Consequently, the HMRC special relief claim is usually filed alongside a full set of missed UK tax returns for every open year, not just the determined ones.
Condition C: A One-Time Relief
Condition C is that you have not claimed HMRC special relief, or the old equitable liability concession, before. HMRC's guidance at SACM12260 says exceptions will be very rare. It does not matter whether the earlier claim succeeded. As a result, HMRC special relief is effectively a once-in-a-lifetime remedy, and it should be used to settle every problem year at once.
Making the Claim and Challenging a Refusal
An HMRC special relief claim is a formal claim outside a return. It needs evidence, and it is decided by a specialist unit rather than your local office.
What the Claim Must Contain
The claim must satisfy the general requirements for claims in Schedule 1A, and paragraph 3A(8) adds that it must include the information reasonably required to decide Conditions A, B and C. In practice, a strong claim contains the completed returns for the determined years, supporting records, a clear explanation of why the notices were missed, and evidence of the correct liability. HMRC's manual at SACM12230 states that the claim must be signed by the person making it and that HMRC's Enforcement Insolvency Service decides it.
The History Behind the Relief
HMRC special relief replaced a non-statutory practice called equitable liability from 1 April 2011, as SACM12210 explains. The relief was put on a statutory footing by the Enactment of Extra-Statutory Concessions Order 2011. The conditions deliberately mirror the old concession, which is why HMRC still treats the relief as exceptional.
How the Tribunal Reviews a Refusal
If HMRC refuses the claim, you can appeal to the First-tier Tribunal. However, the tribunal's role is limited. In Currie v HMRC [2014] UKFTT 882 (TC), the tribunal held that it could only decide whether HMRC's refusal was unreasonable in the judicial review sense, and could not substitute its own view. Later decisions, including Scott v HMRC [2015] UKFTT 420 (TC), followed that approach. Therefore, the claim you submit to HMRC is the case you will be judged on, so it must be complete from the outset.
Montshiwa: A Taxpayer Who Had Left the UK
The leading example for expatriates is Montshiwa v HMRC [2015] UKFTT 544 (TC). Dr Montshiwa, a doctor, returned to Botswana in 2006 and never received the notices to file sent to his UK address. HMRC's determinations totalled £17,121, while his actual liability for the key year was £325.71. The tribunal held that the refusal of HMRC special relief was unreasonable, because the excess was large in absolute and relative terms and HMRC had not properly considered his agent's evidence. The penalties, however, remained. Accordingly, the case shows both what HMRC special relief can achieve and what it cannot.
Penalties, Interest and What Relief Does Not Cover
HMRC special relief reduces tax. It does not automatically remove everything else attached to a missed return.
Late Filing Penalties Survive
Late filing penalties under Schedule 55 to the Finance Act 2009 are charged for failing to file, not for the amount of tax. The fixed £100 penalty, daily penalties of £10 for up to 90 days, and the six-month and twelve-month penalties of the greater of 5% of the tax or £300, all stand unless you have a reasonable excuse. Tax-geared elements fall when the tax falls, because 5% of a smaller figure is smaller, but the £300 minimums remain.
Interest and Payments Already Made
Late payment interest runs on the tax actually due. If HMRC grants the relief, interest is recalculated on the reduced liability. Where you have already paid the determined amount, perhaps to stop enforcement, HMRC special relief can produce a repayment. Condition A expressly covers withholding repayment of an amount already paid. In our experience, paying under protest while the claim is prepared is often sensible where enforcement is imminent.
Enforcement While the Claim Is Pending
HMRC can continue recovery action while the claim is considered. Section 28C(4A) even allows direct recovery from bank accounts to continue if a determination is superseded. Therefore, clients with UK sterling accounts should agree a pause or a time to pay arrangement at the same time as the claim. HMRC's guidance on paying your Self Assessment bill explains the payment routes, including instalment arrangements.
The US Side of an HMRC Determination
UK-focused guides stop here. For Americans, however, the determination and any HMRC special relief claim have direct consequences on the US return.
A Determined Amount Is Not Automatically a Creditable Tax
The US foreign tax credit is limited to the foreign tax you are legally liable to pay. Under the Treasury regulations on creditable foreign taxes in 26 CFR 1.901-2, an amount paid in excess of your actual liability is not a tax if you failed to exhaust effective and practical remedies to reduce it. HMRC special relief is such a remedy where the conditions are met. Consequently, if you pay an inflated determination and never claim relief, the IRS can deny the credit on the excess. The IRS foreign tax credit guidance is built around that principle of compulsory payment.
Foreign Tax Redeterminations After Relief
If you did claim a credit for determined tax and HMRC later reduces it, the change is a foreign tax redetermination. You must notify the IRS by amending the affected US return. Similarly, if the HMRC special relief claim produces returns showing more UK tax in one year and less in another, the US credits for both years move. We therefore prepare the US amendments in the same exercise as the UK claim, so both sides agree.
Missed US Tax Returns at the Same Time
Americans with missed UK tax returns frequently have gaps on the US side as well, particularly after a move. For non-wilful failures, the IRS Streamlined Filing Compliance Procedures remain the standard route. Our IRS Streamlined filing service coordinates those filings with the UK claim. In addition, any UK accounts kept open after leaving remain reportable on the FBAR, as FinCEN's FBAR guidance confirms, and our FBAR and FATCA service handles that reporting.
Case Study: An Executive Who Left London
The following illustrative case study shows how HMRC special relief works in a typical file. The figures are hypothetical but reflect the mechanics we see.
The Facts
Michael is a US citizen and former managing director at a London bank. He left the UK on 30 June 2021 to return to New York, earning £340,000 a year before he left. He kept a London flat, which he let from August 2021 for £3,000 a month. HMRC sent notices to file for 2021/22 and 2022/23 to his old office address. Nobody forwarded them. In October 2024, HMRC issued determinations of £96,000 for 2021/22 and £118,000 for 2022/23, both built on his last full London salary.
Why the Normal Routes Had Closed
Michael discovered the debt in March 2026, when a collection letter reached his New York address. For 2021/22, the displacement deadline was the later of 31 January 2026 and October 2025, so it had passed. For 2022/23, the deadline ran to 31 January 2027, so a return could still replace that determination directly. Therefore, we filed the 2022/23 return in the ordinary way and claimed HMRC special relief only for 2021/22.
The Numbers
For 2021/22, split-year treatment meant only his April to June salary and the rental profit were taxable in the UK. PAYE had already covered most of the salary, leaving about £6,400 of further tax, mainly on the rent. For 2022/23, his UK rental profit of £27,000, with no personal allowance because he held only US nationality, produced tax of about £5,400. The claim explained that the notices had gone to a business address he no longer used, and it enclosed evidence of his departure, the returns and the letting accounts.
The Outcome
In our modelling for files of this kind, HMRC accepts the claim where the evidence is complete, as it was here. The determined total of £214,000 would fall to about £11,800 of tax, plus the fixed and daily late filing penalties and the £300 minimum six-month and twelve-month penalties. On the US side, Michael had claimed no credit for the determined amounts, so no redetermination was needed. However, the UK tax on his rent became creditable against US tax on the same rental income, so we amended his 2021 and 2022 US returns to claim it.
How TaxYork Can Help
TaxYork prepares missed UK tax returns and HMRC special relief claims for Americans in Britain and for Americans who have left. We establish the determination timetable, identify which years can still be displaced by filing, prepare the returns and the evidence pack, and bring every other HMRC matter up to date so that Condition B is met. At the same time, we prepare the US amendments or Streamlined filings, so the foreign tax credit reflects the corrected UK liability.
In addition, our tax treaty optimisation service applies the US-UK treaty to the corrected figures, and our cross-border planning service helps departing clients close their UK affairs properly so that determinations never arise. You can review our full range of US-UK tax services before we speak.
Conclusion
HMRC special relief is narrow, exceptional and available only once. Nevertheless, for an American facing a determination built on a salary they no longer earn, it can reduce a six-figure estimate to the tax that was really due. The claim succeeds or fails on its evidence: why the notices were missed, what the true liability was, and whether every other HMRC matter is now in order.
Therefore, act before enforcement, file every year that can still be displaced in the ordinary way, and reserve HMRC special relief for the years that cannot. Above all, keep the US return in step. An inflated UK determination is not a creditable tax, and a corrected one usually is.
Contact Us
If HMRC has issued a determination you do not recognise, or you have missed UK tax returns after leaving Britain, please book a consultation with our US-UK team. Email hello@taxyork.com or call 020 3488 8606. We will review the dates, the determinations and your US position, and we will set out a clear plan for both sides.
Disclaimer
This article provides general information about HMRC special relief for Americans with missed UK tax returns and related cross-border taxpayers. It does not constitute tax or legal advice for your specific circumstances. UK and US tax rules change frequently, and the case study is illustrative only. You should obtain professional advice based on your own facts before acting. TaxYork accepts no liability for decisions taken on the basis of this article alone.