Tax Services US/UK: A Plain-English Guide to What You Actually Need

This guide maps US/UK tax services to the situations that actually call for them: most people need the two annual returns plus foreign account reporting, and then one specialist service for whatever is unusual about their position. Everything else on a firm's service list is there for someone else's circumstances, not necessarily yours.

Service names vary between firms and tell you very little. The forms behind them do not vary at all. So the useful question when comparing offers is not "do you provide cross-border tax advice?" but "which returns and reports will you file for me this year?"

What tax services do US/UK people actually need?

Start from your own position rather than a brochure. For an American living in the UK, the recurring core is a US federal return, a UK Self Assessment return where HMRC requires one, and US foreign account reporting. For a British person who has moved to the US, the core is a US return plus whatever UK filing continues for UK income, property or pensions left behind.

Specialist services then attach to specific assets or events. A UK investment fund, a pension you have started drawing, a property sale, a business, a gift, an inheritance, a move, or years of missed filings each pull in a particular piece of work. If nothing in that list applies to you, you probably do not need the service being offered.

The annual core: three services most people need

Individual tax returns in both countries

This is the base service: the US federal return with its schedules, any state return, and the UK Self Assessment return with the supplementary pages that apply — including SA109 where residence or the foreign income and gains regime is in point. Double tax relief is part of this work: the foreign tax credit on the US side, Foreign Tax Credit Relief on the UK side. Our individual tax returns page sets out what that covers, and the preparation process shows the order it happens in.

Foreign account and asset reporting

This is the service people most often assume is included when it is not. The FBAR is required where a US person's foreign financial accounts exceeded $10,000 in aggregate at any time in the calendar year, and the IRS states it is filed through FinCEN's BSA E-Filing System and not with your federal tax return. Form 8938 is separate again and is attached to the return, with thresholds that differ depending on filing status and whether you live abroad. See foreign income and FBAR reporting.

UK Self Assessment

Whether HMRC requires a return depends on your income and circumstances, and registration has its own deadline before the filing deadline. The dates are on GOV.UK, and our UK Self Assessment page covers the service.

Specialist services: what attaches to what

Each of these exists because of a specific asset or event. Read the left column, not the service name.

If this is true of you	The service	Typical forms
You hold UK-domiciled investment funds, including inside an ISA	PFIC reporting	Form 8621, the information return for a passive foreign investment company
You are paying into, transferring or drawing a UK or US pension	US/UK pensions	Treaty positions on both returns; US reporting of the scheme
You are relying on a treaty article to change a US result	Treaty relief	Form 8833, Treaty-Based Return Position Disclosure Under Section 6114 or 7701(b)
You are selling or letting UK property	Cross-border property	UK Capital Gains Tax reporting within 60 days; US reporting of the same gain
You are making large gifts, or receiving from abroad	Estate and trust planning	Form 709 for US gift tax; Form 3520 for foreign trusts and certain foreign gifts
You are giving up US citizenship or a green card	Expatriation	Form 8854, Initial and Annual Expatriation Statement
You have not filed US returns for several years	Streamlined catch-up	Back returns and FBARs under an IRS compliance option
The IRS or HMRC has opened an enquiry	IRS representation	Form 2848 for US representation; HMRC agent authorisation

Three of those deserve a note. UK property disposals are on a short clock: GOV.UK states you must report and pay Capital Gains Tax due on UK residential property within 60 days of completing the sale, with interest and a penalty if you are late — that is far tighter than the annual cycle most people plan around. Form 3520 covers transactions with foreign trusts and the receipt of certain large gifts or bequests from foreign persons, which catches people who have inherited from a UK relative. And Form 8854 applies to citizens who have relinquished citizenship and long-term residents who have ended residency.

Planning is a different service from preparation

Preparation reports a period that has closed. Planning changes a decision that is still open: where to hold investments, when to draw a pension, how to time a sale or a move. The two are priced differently and often scoped separately, and it is reasonable for a firm to say that advice on your investment structure is not included in a return-preparation fee.

What is not reasonable is discovering the gap afterwards. If you want the forward-looking view, ask for it by name — see tax planning — and agree what it covers.

Illustrative example: someone moving from London to New York in the spring asks for "tax services" and is quoted for two annual returns. Nobody is asked to look at the timing of a UK property sale or an ISA holding before the move, because neither is part of preparing last year's returns. The returns are filed correctly the following January, by which point the decisions that mattered have already been made. The missing service was planning, and it was missing because nobody named it.

Two positions, two service lists

Abstract lists are hard to judge, so here is what the mapping looks like for two common situations.

An American employed in London

The annual core is a US federal return with the foreign tax credit or the foreign earned income exclusion, a UK Self Assessment return if HMRC requires one, and foreign account reporting once the accounts pass the thresholds. To that, add PFIC reporting if there are UK funds or an ISA holding funds, and pension work once contributions or withdrawals start. Planning matters at three moments: when investing for the first time in the UK, when a share scheme vests, and before any move back. Nothing else on a standard service list is likely to apply until circumstances change.

A British person who has moved to New York

The core is a US return covering worldwide income from the point US residence begins, plus continuing UK filing for UK-source income such as rent, and UK reporting on any property disposal. Pensions left in the UK need treaty analysis before anything is drawn, not after. If a UK house is being let or sold, the property service applies and the 60-day UK reporting clock runs from completion. Catch-up work is rarely needed here, but residence analysis in the year of the move almost always is.

In both cases, the list is three or four items, not ten. That is the normal shape of a cross-border engagement for an individual.

How these services are usually priced

Pricing models differ, and the model tells you something about the scope. Annual filing work is commonly a fixed fee per return, which works because the volume of work is predictable once the documents arrive. Advisory and planning work is more often hourly or a fixed fee per project, because the time depends on the question. Event-driven work, such as a property disposal or an expatriation, tends to be quoted on its own.

Two things are worth asking about whichever model applies: what happens when something new appears mid-year, such as an account, a property or a second country, and whether responding to a tax authority's questions is inside the fee. Neither answer has to be generous — it just has to be written down before you engage, so a surprise later is a conversation rather than a dispute.

Business services, briefly

If you run a company rather than just earning a salary, the list changes: company formation and structure, business tax returns in one or both countries, payroll, and US state-level obligations that have no UK equivalent. Those sit in business tax returns, payroll and multi-state filing. The same rule applies: ask which returns get filed, in which jurisdictions, and by when.

How do you check a service is scoped properly?

A service description becomes real when it turns into a list of filings. Before engaging, get written answers to five questions:

1. Which returns and reports will you file for me this year? Named by form number where one exists.
2. What is excluded? Information returns, state returns and the FBAR are the usual omissions.
3. What triggers an additional fee? A new account, a property, a share scheme event, a move mid-year.
4. Who compiles the account list? The FBAR depends on it, and it should not rely on your memory each year.
5. Does this include representation if a tax authority asks questions? If not, what would that cost?

Those five answers make two quotes comparable. The wider checks on the firm itself are in how to choose US/UK cross border tax specialists, and if you are weighing one firm against keeping an adviser in each country, see one firm or two.

What people get wrong when buying tax services

Buying by list length. A longer service list is not more coverage for you; it is coverage for a wider range of clients. What matters is which items apply to your facts.

Assuming reporting is bundled. The FBAR sits outside the tax return, so it also sits outside a lot of engagement letters.

Treating catch-up as ordinary filing. Missed years are a different service with a different route and different risks, and they are best raised at the first conversation.

Leaving events until the return. A property sale, a pension decision or a move needs attention when it happens, not when the return is prepared months later.

Where to start

Write down your position in five lines: where you live, where your income comes from, what accounts and investments you hold, any pensions, and anything that changed or is about to change. That is enough for an adviser to tell you which services you need and, just as usefully, which ones you do not.

US/UK Cross Border Tax — US CPAs and UK tax advisers working as one team; London, Manchester, New York, San Francisco. Our full range of Tax Services US/UK is set out by service, Americans in the UK covers the most common position, and you can ask for a fee quote listing exactly which returns and reports we would file for you.