High Net Worth US UK Tax Compliance: HMRC's Biggest Bucket

HMRC's Wealthy and Mid-sized Business Compliance directorate held £16.82 billion of tax under consideration at 31 March 2026, and the largest single category was international issues at £4.45 billion. For anyone managing high net worth US UK tax compliance, that number is a map of where enquiry resource sits. It is not a bill, and reading it as one is the first mistake.

The figure comes from the technical note Wealthy individuals and mid-sized business compliance, published on GOV.UK on 9 July 2026 alongside the HMRC Annual Report and Accounts 2025 to 2026. It is the most direct published statement of where HMRC's wealthy-taxpayer pipeline is concentrated. At Jungle Tax we spend most of our year preparing late and corrective US and UK returns for people who sit squarely inside the population that figure describes, so it is worth setting out exactly what it does and does not say.

What the 9 July 2026 technical note actually reports

Three numbers matter, and they measure three different things.

• Compliance yield of £9,962 million for 2025-26. This is HMRC's own estimate of the additional revenue its compliance work generated across the directorate during the year — money actually secured, revenue protected, and future revenue safeguarded by closing down risks.
• Tax under consideration of £16.82 billion at 31 March 2026. This is a snapshot of open work, not a year's collections. It is the aggregate of maximum potential exposures across live risks and enquiries on that date.
• International issues at £4.45 billion. This is the largest single category within that snapshot — larger than the VAT categories taken together (roughly £2.8 billion combined) and more than four times the income and expenses category at £1.04 billion.

Other categories give useful scale. Research and development claims stood at roughly £788 million and pension schemes at roughly £763 million. International is not marginally ahead of the pack; it is in a category of its own.

What does "tax under consideration" actually mean?

This is the part that competitor coverage and press summaries routinely get wrong, and the part a sophisticated reader should insist on getting right.

HMRC's technical note defines tax under consideration as an estimate of the maximum potential additional tax liability in a case, arrived at before HMRC has carried out a full investigation of the specific facts or completed its analysis of the relevant law. The note then says something HMRC does not have to say and which almost nobody quotes: it is not actual tax either owed or unpaid. It is a triage tool, used to point enquiry resource at the largest risks first.

Why the £4.45 billion is not tax owed

Three characteristics follow from that definition and each one cuts the figure down.

• It is a maximum, not an expectation. Each case contributes its worst-case number. Where a risk has several possible readings, the largest goes into the total.
• It precedes the facts. The estimate is formed on incomplete information — often a data match, a mismatch between a return and third-party information, or an unexplained pattern. When the underlying facts are established, a great many cases resolve at a much lower figure, and a substantial number resolve at nil.
• It is a stock, not a flow. The £16.82 billion is what was open on one particular day. Cases enter and leave continuously. Comparing it to a year of collections, as headlines often do, compares two incompatible measures.

So the honest sentence is this: at 31 March 2026, HMRC had international risks on its books whose theoretical ceiling was £4.45 billion. The eventual collected figure will be materially lower. Anyone who tells you that wealthy taxpayers "owe HMRC £4.45 billion on international matters" has misread the source document.

Why the figure still tells you something real

Discounting the number is not the same as dismissing it. Tax under consideration is a genuine and reliable indicator of one thing: where HMRC has chosen to look. Risks do not appear in the pipeline by accident. Each one reflects an analyst deciding that a fact pattern warranted opening or escalating work. A £4.45 billion international book means international fact patterns are, by a wide margin, the most heavily worked category in the wealthy population.

The direction of travel reinforces the point. At 31 March 2025 the same international category stood at approximately £3.17 billion within a total of £14.30 billion. A year later it was £4.45 billion within £16.82 billion. International grew faster than the book as a whole, and its share of the total rose. That is a resourcing signal, and it is the sober inference available from the data.

Why is international the largest category in HMRC's wealthy caseload?

Because international cases are the ones where HMRC's information advantage has grown fastest, and where taxpayer reporting is most likely to be incomplete for reasons that have nothing to do with evasion.

HMRC receives automatic account-level information from financial institutions in over 100 jurisdictions under the Common Reporting Standard, and separately receives and exchanges data under the UK-US intergovernmental agreement implementing FATCA. It holds land registry, employment, pension and investment platform data domestically. When an overseas account, an overseas pension, or an overseas entity interest appears in the data and does not appear on a Self Assessment return, that mismatch generates a risk — and a risk carries a tax under consideration figure from the moment it is opened.

Cross-border fact patterns also generate genuine complexity that produces innocent error at a much higher rate than domestic ones: remittance and foreign income characterisation, double tax relief claims, timing differences between the UK tax year and the US calendar year, foreign entity classification, and the treatment of overseas pensions and investment wrappers. HMRC does not need to allege dishonesty to open a case. It only needs a discrepancy.

Are you inside the population HMRC is describing?

HMRC identifies its wealthy customer population by reference to income of £200,000 or more, or assets of £2 million or more, in any of the last three years. Individuals meeting that test are managed by HMRC's dedicated wealthy teams rather than through general compliance channels, which means their affairs are looked at by specialists with access to the full data picture.

Now overlay the US dimension. A US citizen or green card holder resident in the UK is, almost by construction, an international case in HMRC's terms: overseas citizenship, frequently overseas-source income, often US retirement accounts, sometimes US entity interests, and a reporting footprint that appears in exchanged data. If that person also holds UK investments, a UK pension, or an interest in a UK company, they are simultaneously an international case from the IRS's perspective. The same individual sits in the international bucket of two authorities at once.

This is precisely the population for whom an unresolved filing position — unfiled returns, incomplete disclosure of a foreign account, an omitted information return — is not a quiet private matter. It is a fact pattern that both authorities can see the outline of from their own data.

How the two sides compare for the same taxpayer

Dimension	UK / HMRC	US / IRS
Basis of taxing right	Residence, and for some, domicile-linked rules as reformed for the foreign income and gains regime	Citizenship and lawful permanent residence, regardless of where you live
Annual return	Self Assessment return where a filing requirement arises	Form 1040, filed on worldwide income once thresholds are met
Core foreign asset reporting	Reported through the return itself; no separate universal asset schedule	FBAR (FinCEN Form 114) and Form 8938, with separate thresholds and separate filing mechanics
Typical entity and structure reporting	Disclosed through the return and supporting pages	Forms 5471, 3520 and 3520-A, 8865 and 8621, each with its own penalty regime
Assessment window for offshore matters	Up to 12 years for offshore matters involving careless or innocent error; 20 years for deliberate behaviour or failure to notify	Generally 3 years, extended to 6 years for substantial omissions of foreign income, and unlimited where a required international information return was never filed
Structured route back into compliance	Disclosure through HMRC's published offshore disclosure channels	Streamlined Filing Compliance Procedures, including the Foreign Offshore Procedure for those resident outside the US
Currency and period	Sterling, 6 April to 5 April	US dollars, 1 January to 31 December

The UK side of an unresolved dual filing position

The extended offshore assessment window is the single most consequential UK feature for a US-connected reader. For offshore matters, HMRC's ability to assess reaches back up to 12 years even where the error was careless or genuinely innocent, and up to 20 years where behaviour was deliberate or where a taxpayer failed to notify chargeability at all. Domestic errors carry much shorter windows. The asymmetry is deliberate, and it means an old cross-border omission has a far longer tail than most people assume.

The practical consequence for return preparation is scope. A UK catch-up for a US-connected individual is rarely a one-year or two-year exercise. It requires establishing, year by year, what was reportable, what was reported, and where the gap sits — and doing so across a period long enough that bank records, platform statements and pension documentation frequently need to be reconstructed rather than simply retrieved.

What an international fact pattern looks like in HMRC's data

The recurring shapes we see in UK catch-up work are unglamorous:

• A US brokerage or retirement account that appeared in exchanged data but was never reflected on a Self Assessment return, because the taxpayer assumed a US account was a US matter only.
• Foreign income reported net of US tax without a properly computed double tax relief claim, producing a figure that does not reconcile to the underlying source data.
• An interest in a US LLC or S corporation reported inconsistently, or not at all, because its UK characterisation was never settled.
• Distributions or gains from offshore funds treated on the wrong basis.
• Years in which the individual was UK resident but filed nothing at all, on an incorrect assumption that overseas-taxed income removed the UK filing requirement.

None of these require bad faith. All of them generate a data mismatch, and a data mismatch is exactly what feeds the international category.

The parallel US position for the same taxpayer

A UK-side catch-up that ignores the US side leaves the client half-compliant, and vice versa. The US filing obligation for a citizen or green card holder is not suspended by UK residence or by UK tax paid. It runs continuously.

The return set for a US-connected UK resident with an unresolved position typically includes Form 1040 with the foreign tax credit and foreign earned income exclusion computations, FBAR where aggregate foreign account balances exceeded the reporting threshold at any point in the year, Form 8938 where the higher thresholds applicable to taxpayers living abroad were met, and — depending on holdings — Form 8621 for UK funds and investment wrappers, Form 5471 for interests in UK companies, and Forms 3520 and 3520-A where a foreign trust relationship exists. UK pensions require careful treaty analysis in their own right. The IRS's guidance for taxpayers abroad, and its published pages on FBAR reporting and Form 8938, set out the thresholds and mechanics.

The Streamlined Foreign Offshore Procedure

For a US person who is genuinely resident outside the United States and whose past non-compliance was non-willful, the IRS's Streamlined Filing Compliance Procedures provide the structured route back. The Foreign Offshore stream requires the three most recent years of delinquent or amended income tax returns, six years of FBARs, and a certification of non-willfulness made under penalty of perjury on Form 14653. For those who qualify, the penalty framework that would otherwise attach to late filings and unfiled information returns does not apply.

Two features deserve emphasis for a sophisticated reader. First, eligibility is conditioned on the IRS not having already initiated an examination — the route is available to those who come forward, not to those who are found. Second, the non-willfulness certification is a substantive document, not a formality. It has to describe the actual history truthfully and completely, which means the narrative and the numbers must be built from the same evidence. Our work on IRS streamlined filing is largely evidence assembly before it is form preparation.

Reading the two sides together

The discipline that produces a clean outcome is sequencing the evidence before either return set is drafted. For the US side, that means establishing what the IRS already holds on the account — what returns are recorded as filed, what information returns and third-party data are on file, and where the record is silent. We set out that process in detail in our companion guide on pulling IRS transcripts before a catch-up, and it is the natural counterpart to this piece: this guide tells you where HMRC is looking, that one tells you how to find out what the IRS can already see.

For the UK side, the equivalent exercise is establishing the residence position year by year, the filing history, and the source data behind each year's foreign income and gains. The two evidence sets overlap heavily — the same accounts, the same pensions, the same entities — but they are cut differently by tax year and by currency, and a figure that is right on one return is frequently wrong if transplanted to the other without recomputation.

Where returns are prepared in parallel rather than in isolation, the foreign tax credit position, the treaty positions and the disclosure narratives reconcile to each other. Where they are prepared separately by two unconnected advisers, they very often do not — and an unreconciled pair of filings is itself a discrepancy of the kind that generates risk in both systems.

What the year-on-year movement does and does not prove

It is worth being disciplined about the growth figure too. International tax under consideration rising from roughly £3.17 billion to £4.45 billion in twelve months does not prove that more tax is being evaded, that more taxpayers are non-compliant, or that outcomes have worsened. A rising stock of open risk can reflect more analysts opening more cases, better data matching surfacing more discrepancies, or slower case resolution leaving more work open on the snapshot date. All three are consistent with the same number.

What it does support is narrower and more useful: HMRC has more international work open than a year ago, that work is a larger share of its wealthy caseload than a year ago, and the category is growing faster than the whole. If your fact pattern is international, the probability that it is looked at has risen. That is the whole of the honest inference, and it is enough.

Three misreadings worth avoiding

• "HMRC says wealthy taxpayers owe £16.8 billion." It says no such thing. That is the ceiling on open risk, expressly stated not to be tax owed or unpaid.
• "Compliance yield of £9,962 million is the amount recovered from evaders." Compliance yield is a composite measure that includes revenue protected and future liabilities prevented, across a population where most cases involve error rather than fraud.
• "The international figure means offshore evasion." International in this context means cross-border fact patterns. The category captures complexity and mismatch at least as much as concealment — which is precisely why an ordinary dual filer with an incomplete history is inside it.

Where this leaves a US-connected UK resident

If you are a US citizen or green card holder resident in the UK with an unresolved filing position, the right conclusion from the 9 July 2026 technical note is not alarm. It is that your fact pattern belongs to the category both tax authorities have chosen to resource most heavily, and that the correct response to that is accurate, complete, well-evidenced returns on both sides — prepared once, prepared properly, and reconciled to each other.

You can read HMRC's own published account of how it approaches this population in the wealthy individuals and mid-sized business compliance technical note on GOV.UK, and its wider guidance on tax on foreign income. Our own UK tax services and US-UK tax accountants pages set out how we handle both return sets in a single engagement, and further reading sits in our guides library.

If you have years outstanding, an incomplete disclosure history, or two sets of returns that have never been reconciled to each other, the work is specific, finite and best done once. To discuss your position in confidence, contact our cross-border team for a confidential consultation. We will tell you plainly what the scope looks like, what evidence we need, and what a complete, defensible filing position on both sides of the Atlantic requires.