HMRC One to Many Letter: Your US-Source Income Explained

An HMRC one to many letter about US-source income is a data-driven prompt, not an enquiry. HMRC has received information showing you hold US dividends, a US rental property, a US partnership interest or US trading income, and cannot reconcile it with your Self Assessment return. Your reply decides whether the file closes or escalates.

Why this particular letter is different from the standard offshore nudge

Most commentary on HMRC's one to many campaigns describes the generic "we believe you may have overseas income or gains" letter, driven by Common Reporting Standard data. The US-source version is a different animal, and the difference matters enormously for how you answer it.

The United States is not a CRS participating jurisdiction. It never adopted the OECD standard, and no US bank or broker reports to HMRC under CRS. So when a letter lands referring specifically to income arising in the United States, the data behind it did not come through the ordinary offshore channel. It came through one of a small number of narrower pipes, and each of those pipes tells you something precise about what HMRC is looking at.

That distinction is what most generalist guidance misses. A response drafted on the assumption that HMRC has seen a bank balance is the wrong response when what HMRC has actually seen is a gross dividend figure with federal tax withheld at source, or a partnership distribution subject to withholding on effectively connected income. At Jungle Tax we see these letters regularly among UK-resident Americans and UK residents holding legacy US assets, and the pattern of what HMRC knows is remarkably consistent.

What triggers an HMRC one to many letter about US income?

HMRC's Connect system compares third-party data against the boxes on your return. A mismatch, or an absence where data suggests there should be an entry, generates the letter. For US-source income the third-party data typically arrives by one of these routes.

Reciprocal exchange under the FATCA intergovernmental agreement

The UK was the first country to sign a FATCA IGA with the United States, and it is a reciprocal Model 1 agreement. UK financial institutions report US persons to HMRC, which passes the data to the IRS. Running in the opposite direction, the US Treasury provides HMRC with information on certain US-source income paid to UK-resident account holders. In practice this has covered US-source interest and dividends credited to accounts identified as belonging to UK residents.

Article 27 exchange of information under the US-UK treaty

Separately from FATCA, Article 27 of the US-UK Double Taxation Convention permits exchange of information that is foreseeably relevant to administering either country's tax law. Bulk data on US investments held by UK residents has been supplied under this authority. The practical consequence is that HMRC can hold gross income figures for you even where no FATCA report was filed, and can request specific information about a named taxpayer on request from the IRS.

US withholding documentation

Where a US payer treats the recipient as a foreign person, it issues Form 1042-S rather than a 1099, showing gross income by income code and the federal tax withheld. Publicly traded partnerships also report distributions of effectively connected income this way. See the IRS's own description of Form 1042-S. These forms carry a foreign address and, increasingly, a foreign taxpayer identification number, which is precisely the field that makes the data matchable to a UK Self Assessment record.

Real-estate and disposal reporting

Sales of US real property by non-US persons attract withholding under the FIRPTA rules and generate their own reporting trail. Rental agents and property managers making payments to a foreign owner also withhold and report unless a net-basis election is in place. Either event can surface a US property that has never appeared on your UK foreign property pages.

The mismatch HMRC is actually testing

What HMRC has seen	Likely source of the data	What HMRC infers if your return is silent
Gross US dividends and federal tax withheld	FATCA reciprocal reporting; Article 27 bulk exchange	Foreign dividend pages omitted, or reported net of withholding
Gross rents paid to a foreign owner, tax withheld	US withholding agent reporting on Form 1042-S	US property never entered on the UK foreign property pages
Partnership distribution of effectively connected income	Partnership withholding and 1042-S reporting	Undeclared partnership profit share, not just the cash drawn
Proceeds of a US real property disposal	FIRPTA withholding and associated reporting	Unreported chargeable gain, possibly in a closed-looking year
US-source business or service income	Payer reporting; treaty partner request	Trading profits under-declared on the self-employment pages

Why your US filing does not answer the letter

This is the single most common and most expensive misunderstanding. Clients arrive holding a complete, professionally prepared Form 1040 with the US-source income properly reported and tax paid, and reasonably assume that a copy of it is a full answer. It is not, for six structural reasons.

• The UK taxes you as a resident, not as a source country. A UK resident is chargeable on worldwide income as GOV.UK confirms. US-source income belongs on your UK return regardless of how much US tax was paid. Payment of US tax is a credit question, not an exclusion question.
• The measure of profit differs. A US Schedule E rental profit is computed after depreciation. Depreciation on residential buildings has no UK equivalent, so the UK taxable profit is typically higher. Financing cost relief also differs: the UK restricts finance costs on residential lets to a basic-rate tax reduction, while the US allows a deduction against rental income. Handing HMRC a Schedule E figure invites a challenge you will lose.
• The tax years do not align. The US year ends 31 December; the UK year ends 5 April. Any reconciliation must be re-cut to the UK basis period, with a clear explanation of the apportionment method used.
• Currency conversion is a live issue. Income must be converted at an appropriate rate. Applying a single year-end rate when HMRC expects a monthly or transaction-date basis produces a difference that looks like an under-declaration.
• Credit relief is directional and capped. The credit HMRC allows is limited to the tax the US may charge a UK resident under the treaty, not the tax you actually paid as a US citizen. HMRC's own Double Taxation Relief Manual guidance on the United States sets out the point directly: the UK will not relieve US tax charged solely by reason of the saving clause in Article 1(4). For a portfolio dividend, HMRC will generally allow the treaty rate, not your marginal US rate. See also HMRC's International Manual on portfolio shareholders.
• The excess US tax is relieved on the other side. Where US tax exceeds what the treaty permits the US to charge a UK resident, the answer is not a bigger UK credit. It is the resourcing mechanism in the treaty, which allows the excess to be relieved against US tax on the US return via the foreign tax credit. Many US returns prepared without UK input never make this claim, which is why the same income is genuinely over-taxed and the reply to HMRC becomes an opportunity as well as an obligation.

How the four income types actually behave across the two systems

US dividends and interest

A US citizen cannot lodge a Form W-8BEN with a US broker, so a properly documented US-citizen account produces 1099s and no withholding. Problems begin when a broker has treated the account as foreign because of the UK address, and has withheld at a treaty or statutory rate. You then have withholding that HMRC can see, on income you may have reported to the IRS gross, and possibly no UK entry at all.

On the UK side, foreign dividends go on the foreign pages with credit relief claimed. HMRC expects you to have minimised the foreign tax available for relief, meaning it will restrict the credit to the treaty rate for portfolio dividends even where a higher rate was suffered. The over-withheld element is recovered from the IRS, not from HMRC. Interest is treated more starkly still: the treaty generally allocates taxing rights on interest to the residence state, so credit expectations on US-source interest should be set carefully.

A US rental property

This is the type that most often produces a genuine, sizeable under-declaration. UK-resident owners frequently believe that because the property is in America and US tax has been paid, the matter ends there. The UK charges the profit on a UK-computed basis, and the property must appear on the foreign property pages every year it is let, including years of loss.

Practical points that decide the outcome: US losses cannot be surrendered against UK income of other types, and UK property losses carry forward within the property business; US state income tax on the rental is generally outside the scope of the federal-level treaty, so the relief position for state tax needs to be examined rather than assumed; and where a net-basis election has been made on the US side, gross withholding stops but the reporting trail does not.

A US partnership or LLC interest

Partnership interests generate the most technically difficult letters. Three issues compound.

• Cash drawn is not the taxable amount. You are taxable on your profit share, in both countries, whether or not distributed. HMRC may have seen a distribution figure and be reasoning backwards to a much larger allocated profit.
• The K-1 arrives late. Partnership reporting frequently lands after the UK filing deadline, and after any extended US deadline. Provisional UK figures with a clear note, followed by amendment, is a defensible approach; silence is not.
• Entity classification can diverge. Whether a US LLC or partnership is transparent for UK purposes is fact-sensitive and turns on the constitutional documents and the members' rights. Getting this wrong changes the entire character of the income and the availability of credit relief. This is a question to settle with cross-border advice before writing to HMRC, not after.

US-source trading and professional income

Under the business profits article, the US may generally only tax the business profits of a UK-resident enterprise where there is a US permanent establishment. A UK-resident consultant billing US clients from London often has no US taxing right at all, which means US tax suffered may be recoverable rather than creditable. Separately, self-employment tax is a social security charge, not an income tax, and the US-UK totalization agreement governs which country's system applies. Self-employment tax is not creditable against UK income tax, and a certificate of coverage may remove it entirely.

US versus UK treatment at a glance

Issue	US treatment	UK treatment	Where the letters go wrong
Tax year	Calendar year to 31 December	6 April to 5 April	US figures transcribed without re-cutting to the UK year
Rental profit	Depreciation deductible over a statutory life	No depreciation for residential buildings	Schedule E profit used as the UK figure
Residential finance costs	Deductible against rental income	Basic-rate tax reduction only	UK profit understated
Portfolio dividends	Taxed on the 1040; withholding may apply if treated as foreign	Foreign pages; credit generally limited to the treaty rate	Full US tax claimed as UK credit
Partnership income	Allocated profit share taxed, K-1 reported	Profit share taxed; entity transparency must be established	Only cash distributions declared
Excess US tax	Relieved by resourcing income and claiming credit on the 1040	Not relievable by HMRC beyond the treaty rate	Claim never made, genuine double taxation left in place
Social charges	Self-employment tax governed by the totalization agreement	Not creditable against income tax	Treated as creditable foreign tax

Should you sign the certificate of tax position?

Many one to many letters enclose a certificate of tax position with tick-box declarations. There is no legal obligation to complete or return it, and professional bodies have consistently advised against doing so. The certificate is open-ended and undated in scope: it invites you to certify a position across your entire tax affairs, not merely the US income the letter concerns. Signing it converts a narrow data query into a broad self-certification, and an inaccurate certificate carries the risk of a criminal, rather than civil, characterisation of any later-discovered error.

The better course is a substantive letter that answers the actual question, sets out the figures, and evidences them. That approach is more informative to HMRC than the certificate, and it keeps the boundaries of the exchange where they should be.

What a considered response actually contains

A strong reply is short in tone and thorough in substance. Before anything is sent, the work happens behind it.

• Reconstruct the US position from source documents. Gather every 1099, 1042-S, K-1 and closing statement for the years in scope, not the tax return summaries. HMRC's figure is a gross figure from a payer; your reconciliation must start from the same place.
• Rebuild the income on a UK basis. Re-cut to 6 April year ends, convert at a defensible rate, strip out depreciation, restate finance costs, and identify the correct UK box for every item.
• Fix the credit position. Establish the treaty rate the US was entitled to charge, compare it with what was actually suffered, and identify whether the excess is recoverable from the IRS or relievable by resourcing on the US return.
• Quantify the difference before you write. Never open a correspondence you have not already modelled. If there is an under-declaration, you should know its size, the years affected, and the likely penalty behaviour category before HMRC does.
• Choose the right channel. If the return was correct, a reasoned letter with a schedule of reconciliation is the answer. If it was not, the correction usually belongs in the Worldwide Disclosure Facility, which requires notification followed by a 90-day window to complete the disclosure, extendable in complex cases.
• Answer only what was asked. Provide the reconciliation for the income identified. Do not volunteer an unprompted tour of the rest of your affairs, and do not attach documents whose relevance you have not considered.
• Agree the timetable rather than miss it. The typical 30-day window is administrative. Where a K-1 or a broker reissue is outstanding, write within the period to agree an extended date. A reasoned request is almost always accommodated; silence is not.

How do you respond without opening a wider enquiry?

The letter is not an enquiry, and HMRC has no open statutory window merely because it wrote to you. What converts a nudge into an enquiry is usually one of four things: no reply at all; a reply that contradicts data HMRC already holds; a reply that discloses a problem without quantifying or correcting it; or a signed certificate that later proves inaccurate.

The discipline, then, is precision. State the position, evidence it, correct anything that needs correcting through the proper channel, and close the loop in one exchange. Where the UK position turns on an entity classification or a treaty article rather than a number, say so plainly and set out the analysis, because a well-reasoned technical position that HMRC can read and accept is far cheaper than one it has to extract.

What if there is a real under-declaration?

Offshore matters carry an extended assessing window and an enhanced penalty regime, and the multipliers for offshore non-compliance are materially higher than for domestic errors. Behaviour is the variable that matters most: whether the failure is characterised as careless or deliberate, and whether the disclosure is unprompted or prompted, drives the penalty band far more than the size of the tax. A nudge letter means any subsequent disclosure is prompted, which is precisely why the quality and completeness of the first response carries so much weight.

Deal with the US side in parallel rather than afterwards. If the US-source income was correctly reported to the IRS but the credit claim was never optimised, an amended return may recover tax. If US filings are themselves incomplete, the correction belongs in the appropriate IRS programme, and our IRS streamlined filing specialists can run that alongside the UK disclosure so the two sets of numbers agree. Nothing damages a position faster than a UK disclosure that contradicts a US return filed three months later.

Common mistakes we are asked to unwind

• Replying by telephone, so that no controlled record of what was said exists.
• Sending the Form 1040 as the answer, inviting HMRC to compute UK profits from US figures.
• Declaring net-of-withholding income, which understates the gross HMRC already holds and looks deliberate.
• Claiming full US tax as UK credit, which HMRC restricts and which then colours the whole exchange.
• Correcting one year quietly and leaving the rest, which HMRC's data will surface anyway.
• Signing the certificate to make the letter go away.

A structured review of the whole position, rather than a reactive reply, is usually the better investment. Our US-UK tax accountants handle the UK reply and the US return as a single piece of work, and high-net-worth clients with multiple US income streams often find the exercise recovers more in unclaimed relief than it costs. For the wider planning context, see our cross-border tax planning service and our library of technical guides.

Speak to us before you reply

A one to many letter about US-source income is a narrow, answerable question, and it stays narrow only if the first reply is right. If a letter has arrived, or you suspect one will, contact our cross-border team for a confidential consultation. We will reconstruct the US and UK positions, quantify any exposure before HMRC does, correct both sides in step, and draft a response designed to close the matter rather than extend it.