US Tax Preparation for American Expats: UK Business Visitors

An American executive payrolled in the United States who performs employment duties in the United Kingdom creates a UK PAYE obligation for the UK host entity from the first workday. An HMRC short-term business visitor agreement — the EP Appendix 4 arrangement — relaxes that real-time operating requirement where strict treaty, employer and cost conditions are met, and substitutes an annual report instead.

That relaxation is the single most misunderstood mechanism in US tax preparation for American expats who are not, in any ordinary sense, expatriates at all. They live in Greenwich or Palo Alto, they are on a US payroll, they hold a US passport, and they fly to a London group company six, ten or twenty times a year. Nothing about their life feels cross-border. Their tax position is. At Jungle Tax we see the same file repeatedly: years of UK workdays that were never reported by anyone, a US return that claimed no foreign tax credit because no UK tax was ever assessed, and a UK group entity that has just been asked by HMRC to explain both.

Why UK duties create a PAYE obligation from day one

UK income tax on employment income follows where the duties are performed, not where the payroll sits and not where the employment contract was signed. A non-resident individual performing duties in the UK has UK-source employment income for those days. The domestic PAYE regulations then reach the entity that is, in substance, the employer for whom the work is being done — including a UK company hosting an employee whose formal contract is with an overseas affiliate.

There is no de minimis in the legislation. A single day of UK duties is a day of UK-source employment income and, absent relief, the UK host entity is expected to operate PAYE on the proportion of pay attributable to it. Executives find this counter-intuitive because nothing changes on the US side: the W-2 is unaffected, the US withholding continues, and no UK payslip is ever produced. The obligation exists regardless.

Two things can switch it off. The first is the treaty. The second is HMRC's administrative machinery for applying the treaty without a monthly payroll run — the Appendix 4 agreement. They are not the same thing, and conflating them is the root of most exposure we are asked to clean up.

What treaty article does the Appendix 4 relaxation actually rest on?

The relaxation rests on the income from employment article of the relevant double taxation agreement — historically and in OECD Model terminology the dependent personal services article. In the current US–UK treaty this is the Income from Employment article; in the OECD Model it is Article 15. Practitioners still use the older label because HMRC's own guidance does. The article number in the specific treaty in point should be confirmed before it is cited in correspondence.

The article operates in a single direction: it gives the individual's country of residence exclusive taxing rights over employment income earned on visits to the other state, provided three conditions are met together. Fail any one, and the host state's ordinary taxing right revives in full.

• Presence. The individual is present in the host state for no more than a stated number of days in the relevant measuring period. The number and the period — whether a tax year, a calendar year, or any rolling twelve months — vary between treaties and must be read from the treaty itself, not assumed.
• Employer. The remuneration is paid by, or on behalf of, an employer who is not a resident of the host state.
• Cost. The remuneration is not borne by a permanent establishment the employer has in the host state.

HMRC's published criteria for the Appendix 4 arrangement, set out in its PAYE Manual guidance on EP Appendix 4, track those conditions closely and add a practical overlay about what the UK entity must be able to evidence and when.

The condition that actually fails: cost, not days

Every generalist article about short-term business visitors leads with the day count. In our experience of preparing catch-up filings for US executives, the day count is rarely the condition that breaks. The cost condition is.

Intercompany arrangements inside a group are designed for transfer pricing, not for payroll relief, and the two pull in opposite directions. Transfer pricing wants the UK entity to bear the economic cost of services it benefits from. The treaty's employment article wants the UK entity not to bear the remuneration cost of the visiting employee. A management charge, a cost-plus service fee computed on a cost base that includes the visitor's compensation, a project recharge, a cross-charge for time booked to a UK cost centre — any of these can mean the remuneration is, in substance, borne in the UK. HMRC looks at economic reality rather than the label on the invoice.

This is the economic employer question. Who directs the work? Who bears the risk and reward of it? Who takes the output? Where a US executive spends recurring blocks of time integrated into a UK business unit, reporting into UK management on UK deliverables, the UK entity can be the economic employer even though the contract, the payslip and the withholding are all American. Where the visitor is in the UK only very briefly, HMRC has historically applied a light-touch administrative approach and not pressed the economic employer analysis — but that concession has a day threshold attached, that threshold has been the subject of consultation and change, and its current form must be confirmed rather than assumed from an older article.

The practical consequence is stark. A senior executive who spends a modest number of days in the UK but whose compensation feeds a cost-plus recharge to the UK entity may sit outside the Appendix 4 arrangement entirely, while a colleague who spends more days in the UK but whose cost is genuinely retained in the US sits comfortably within it. Day count alone tells you nothing.

What the UK entity actually owes: the annual report

An Appendix 4 agreement is not automatic. The UK entity applies to HMRC for it, and once agreed it replaces real-time PAYE operation for covered visitors with a single annual report filed after the UK tax year ends on 5 April. The filing deadline commonly cited is 31 May following the end of the tax year; the current date should be confirmed against HMRC's live guidance before a submission is planned around it.

The report is banded by presence. The bands themselves are the core of the compliance burden, and the day figures that define them must be verified against HMRC's current published criteria — they have moved, and secondary sources go stale quickly.

• Lowest band. Minimal detail. Broadly, the entity confirms the number of individuals and that they were paid from a non-UK payroll. The economic employer analysis is not pressed at this level.
• Middle band. Named reporting. Name, home country, dates of arrival and departure, UK workdays, and an estimate of UK earnings for each individual. The cost condition must be satisfied and evidenced.
• Upper band. Everything in the middle band plus a certificate of residence, or equivalent evidence of treaty residence, from the home tax authority.
• Above the arrangement. Beyond a further threshold, the individual cannot be covered by the arrangement at all and UK payroll operation, or a specific application to HMRC, becomes necessary.

Three further points are routinely missed. First, the arrangement covers income tax only — National Insurance sits under a separate regime and, for a US executive, is normally addressed by a certificate of coverage under the US–UK social security agreement rather than by Appendix 4. Second, the arrangement does not cover UK statutory directors, whose position is different and stricter. Third, a separate PAYE special arrangement exists for visitors from countries with no treaty, or from overseas branches, where Appendix 4 cannot apply — it is an annual settlement of tax, not a relaxation, and it carries its own day limit.

US versus UK: what each side actually asks of the same trips

Question	UK / HMRC position	US / IRS position
Does the trip create a filing obligation?	Yes in principle — UK-source employment income arises from day one of UK duties	No new obligation — a US citizen or resident already reports worldwide income annually
Who carries the primary obligation?	The UK host entity, through PAYE or the Appendix 4 report	The individual, on Form 1040
What relieves double taxation?	Treaty exemption where all employment-article conditions are met	Foreign tax credit for UK tax properly imposed on UK workdays
Measuring period	UK tax year, 6 April to 5 April	Calendar year
Does the trip reduce tax owed?	May remove UK tax entirely if the treaty conditions hold	No — US tax on worldwide income is unchanged; only the credit position moves
Key evidence	Travel calendar, payroll source, intercompany agreements, certificate of residence	Workday allocation, UK tax assessed and paid, dates of payment, treaty position
Consequence of silence	Employer-level PAYE exposure, interest and penalties, often grossed up	Lost or time-barred credits, and penalties where information returns were missed

The US return: the trips do not reduce US tax, but they can move the credit

A US citizen is taxed on worldwide income wherever earned and wherever resident. UK business trips do not shelter income, do not reduce the W-2, and do not create an exclusion — the foreign earned income exclusion depends on residence or physical presence abroad that a frequent business traveller does not have. What the trips do is change the source of a slice of compensation.

Compensation for services is sourced where the services are performed, apportioned on a workday basis. Days worked in the UK generate foreign-source compensation. If UK tax is properly imposed on those days — because the Appendix 4 conditions were not met, or because the individual crossed into UK residence, or because a recharge defeated the treaty — that UK tax becomes a creditable foreign income tax, claimed on Form 1116 in the general category. The IRS sets out the framework on its foreign tax credit guidance, and the mechanics of the limitation on Form 1116.

Why the two returns must tell the same story

The credit is limited by reference to foreign-source taxable income. That means the workday numerator you use to compute foreign-source compensation on the US return should be the same workday figure the UK entity reported for you, or that you used to compute your UK liability. Where the UK side used one calendar and the US side used another — and this happens constantly, because the UK side counts presence for treaty purposes and the US side counts workdays for sourcing — the returns diverge, and a later enquiry on either side exposes the inconsistency.

Build one master travel record and drive both filings from it. It should distinguish, for every trip: date of arrival, date of departure, days of presence, days on which duties were actually performed, non-working days, travel days, and the UK entity and cost centre the work was for. That last column is what answers the cost-recharge question years later.

Timing: two tax years that do not line up

The UK tax year ends on 5 April and the US year on 31 December. A UK liability arising in respect of UK duties may be assessed and paid in a period that straddles two US tax years. Whether the credit is claimed by reference to when the foreign tax accrued or when it was paid depends on the election in force, and once a taxpayer elects the accrual method that election is generally binding for later years. Where UK tax is paid late — which is exactly what happens in a catch-up — the interaction with the US limitation period for claiming or adjusting a foreign tax credit becomes the controlling deadline. It is frequently the reason a catch-up must be sequenced in a particular order rather than filed all at once.

What happens when no agreement was ever in place?

This is the position we are most often engaged on. There is no Appendix 4 agreement, there never was, and several years of UK workdays by US-payrolled executives sit entirely unreported. Sometimes the trigger is an HMRC employer compliance review. Sometimes it is a new group tax director running a travel-data report for the first time. Sometimes it is a transaction, and a buyer's diligence questionnaire asks the question nobody has asked internally.

The exposure has two faces that must be handled separately but in a coordinated way.

• The UK entity's exposure. A failure to operate PAYE is an employer failure. HMRC's assessment is against the employer, not the employee, and because the employee was paid gross the tax due is typically computed on a grossed-up basis — the settlement is materially larger than the tax that would have been withheld had payroll run correctly. Interest runs from the original due dates. Penalties depend on HMRC's view of behaviour, and an unprompted disclosure is treated very differently from one made after an enquiry has opened.
• The individual's exposure. Where the treaty genuinely protected the visitor, the individual may have no UK liability at all even though the employer failed procedurally. Where it did not — the recharge point again — the individual may need to be brought into UK self assessment for the relevant years, and the UK tax then needs to be reflected as a credit on amended US returns.

Retrospective application is not a reliable route. An Appendix 4 agreement is prospective in character; it is not a way of curing historic years by applying for it now. The historic years are dealt with by disclosure and settlement, and the agreement is put in place to stop the exposure recurring. Our UK tax services team runs the UK-side disclosure while the US-side amendments are prepared in parallel, because the two have to agree on numbers before either is filed.

The catch-up sequence when the individual also has unfiled US years

A meaningful minority of these executives have a second problem. They are dual nationals, or they moved to the US years ago and were never told their UK accounts still needed reporting, or they hold a legacy UK pension or ISA. The business-travel issue surfaces the wider position, and both have to be resolved together without one prejudicing the other.

1. Build the factual record first. Travel calendars, passport stamps, expense system extracts, corporate travel bookings, badge-in data, and calendar exports. Reconstruct workdays by entity and cost centre for every open year. Nothing is filed until this is stable, because everything downstream depends on it.
2. Test the treaty year by year. Presence, employer, and cost tested separately for each year. The answer changes between years far more often than clients expect, usually because an intercompany agreement was renegotiated.
3. Quantify the UK position. Employer-level exposure on a grossed-up basis; individual-level liability where the treaty fails. Determine whether disclosure is employer-led, individual-led, or both.
4. Assess the US filing history. Establish whether US returns, FBARs and Forms 8938 were filed for the open years, and whether the non-compliance was non-wilful. If years are missing, a structured catch-up through the IRS streamlined filing procedures is usually the appropriate route — but eligibility is fact-specific and is tested before anything is submitted.
5. Sequence the filings. UK tax must generally be assessed and, in most cases, paid before it can be claimed as a foreign tax credit on the US side. Filing the amended US returns first, on estimated UK numbers, usually means filing them twice.
6. File, then fix forward. Put the Appendix 4 agreement in place, implement a travel-tracking process, and align the intercompany recharge documentation with the treaty position so the same problem does not regenerate next year.

The documentation pack that settles the question

When HMRC or the IRS asks, the answer is evidential, not argumentative. A defensible file for each executive and each year contains the travel calendar reconciled to an independent source, the employment contract and any assignment letter, payroll evidence showing who paid the compensation, the intercompany agreements and the computation of any management charge or cost-plus fee including whether the individual's compensation entered the cost base, a certificate of residence where the band requires one, the UK entity's Appendix 4 submission, and the US return showing the workday allocation and the credit claimed. Most groups can produce two of those seven on request. Assembling the other five after the fact is the work.

Where the same executive also holds UK pensions, investment accounts or property, the reporting overlay is wider than employment income alone, and our cross-border tax compliance team scopes that at the outset rather than discovering it mid-disclosure. For senior individuals with complex positions across both systems, our private client practice handles the whole return-preparation cycle on both sides.

What good looks like going forward

The groups that never have this conversation do three unremarkable things. They capture business travel at the point of booking rather than reconstructing it in May. They review intercompany recharge mechanics annually against the treaty conditions rather than treating transfer pricing and employment tax as separate files. And they identify, before the trips start, which executives are close to a band boundary so the reporting position is known in advance rather than discovered afterwards.

None of that is sophisticated. It is simply the difference between an annual report and a multi-year disclosure.

Speak to us in confidence

If your UK workdays were never reported, if an Appendix 4 agreement was never applied for, or if you are preparing US returns for executives whose UK travel has never been quantified, the position is almost always better resolved before anyone asks. We prepare the returns and the disclosures on both sides of the Atlantic, we sequence them so the foreign tax credit is not lost, and we do it without drama. Contact our cross-border team for a confidential consultation, and we will tell you plainly what the exposure is and what it takes to close it.