US Tax Return Preparation for Expats: The London Standard

Great US tax return preparation for expats is visible on the page. A correctly prepared Form 1040 for an American living in London carries a specific, predictable stack of schedules and international forms. If yours is four pages long, it is almost certainly incomplete — and you can prove that yourself in under twenty minutes.

This guide is a forensic anatomy of what a properly prepared London return should actually contain. Open last year's PDF alongside it. We are not describing an aspirational standard; we are describing the minimum a competent cross-border preparer produces for a UK-resident US citizen with a salary, a workplace pension, a stocks and shares ISA, perhaps a flat let out, and possibly a UK company. Jungle Tax reviews dozens of these returns every year, prepared by everyone from high-street UK accountants to large US chains, and the failure patterns are remarkably consistent.

What does great US tax return preparation for expats actually look like?

A well-prepared expat return does four things that a domestic-style return does not. First, it makes an explicit, documented choice between the foreign earned income exclusion and the foreign tax credit rather than defaulting to whichever the software suggests. Second, it reports every UK financial account and asset across the correct three places — FBAR, Form 8938 and Schedule B Part III — and those three agree with each other. Third, it characterises UK investments correctly, which in practice means confronting the PFIC problem rather than ignoring it. Fourth, it aligns with the UK Self Assessment position so that HMRC and the IRS are being told a consistent story.

Weak returns fail on all four. They typically show a single Form 2555, no Form 8938, no Form 8621, unanswered Schedule B questions, and a UK pension treated as though it were a US 401(k) by accident rather than by treaty analysis. That return is not merely suboptimal — it is frequently understated, and understatement on an international information return is what keeps the assessment window open indefinitely.

The page count test

Before you read a single number, count the forms. A single American in London earning a City salary, contributing to a workplace pension, holding an ISA and two current accounts, should have a return running to roughly fifteen to thirty pages once the international forms are attached. A return of six pages is a signal, not a proof — but it is a strong signal.

Form 2555 or Form 1116 — and why a London return showing only Form 2555 is usually wrong

The foreign earned income exclusion on Form 2555 lets a qualifying expatriate exclude a capped amount of foreign earned income — approximately $130,000 for the 2025 tax year and around $132,900 for 2026, with a separate foreign housing exclusion on top. It is intuitive, it is cheap to prepare, and for an American in a low-tax jurisdiction it is often correct. For an American in London it frequently is not. The IRS explains the mechanics on its foreign earned income exclusion page.

The UK is a higher-tax jurisdiction than the United States across most of the income range once the 40% and 45% bands bite and the personal allowance tapers away above £100,000. That means UK tax paid on your salary, claimed as a credit on Form 1116, will usually wipe out the entire US liability on that salary and generate excess credits. Those excess credits carry back one year and forward ten. They are a real, valuable asset — and Form 2555 destroys them, because foreign taxes attributable to excluded income are not creditable.

Why this matters more than the tax saved this year

Excess general-basket credits are what shelter a future US-taxable event that the UK does not tax the same way: a lump sum, a bonus paid after departure, a US-source capital event, an exercise of options straddling both systems. An expat who spent a decade on Form 2555 arrives at that event with nothing banked. Worse, revoking the section 911 election has consequences — once revoked, you generally cannot re-elect for five tax years without IRS consent. A good preparer documents that decision in writing at the time. A weak one silently ticks a box in software.

How the foreign tax credit should actually be built for a UK taxpayer

Look for these features on the Form 1116 pages of your return:

• More than one Form 1116. Foreign taxes are separated into categories — general (your salary), passive (UK bank interest, dividends, most investment income), foreign branch, section 951A and treaty-resourced. A London return with employment income and UK investment income needs at least two Forms 1116. One is a red flag.
• Schedule B to Form 1116 attached. This is the carryover reconciliation schedule. If your preparer is not tracking your unused credit balance year on year, they are throwing away money and you will never know.
• A conscious paid-versus-accrued election. The UK tax year runs 6 April to 5 April; the US tax year is the calendar year. On the cash (paid) basis, a US calendar year picks up PAYE deducted in that calendar year plus any Self Assessment balancing payment made in it — which may relate to an entirely different UK year. On the accrued basis, foreign taxes are matched to the income year they relate to. The accrual method is usually cleaner for a UK taxpayer, but it is binding for all future years. Ask which one was used and why.
• UK tax apportioned, not lumped. A single PAYE figure dropped into the general basket is wrong if part of your UK tax relates to dividends or interest. Correct apportionment is fiddly, manual, and precisely what you are paying for.

US versus UK treatment of the assets a London American actually holds

Asset or income source	UK / HMRC treatment	US / IRS treatment on a correctly prepared return	Where it should appear
Stocks & shares ISA	Tax free; nothing reported on Self Assessment	Fully taxable; underlying funds are usually PFICs	Schedule B, Form 8621 (one per fund), Form 8938, FBAR
Cash ISA	Tax free interest	Ordinary interest income at marginal rates	Schedule B Part I, Form 8938, FBAR
UK workplace pension or SIPP	Relief on contributions; growth untaxed	Growth generally not currently taxed under the treaty; contributions require analysis	Form 8938, FBAR (usually), Form 8833 where a position is taken
25% pension commencement lump sum	Tax free up to the applicable allowance	Generally taxable to a US citizen; the treaty lump-sum article is caught by the saving clause	Form 1040 pension lines; Form 1116 where UK tax arises
Main residence gain	Usually exempt under private residence relief	Only the section 121 exclusion applies; excess taxable, plus possible FX gain on mortgage repayment	Schedule D, Form 8949, section 988 computation
UK buy-to-let	Finance costs restricted to a basic-rate credit	Mortgage interest fully deductible; foreign property depreciated under ADS	Schedule E, Form 1116 (passive)
UK limited company you control	Corporation tax; dividends taxed on extraction	Controlled foreign corporation; GILTI inclusion possible before any dividend	Form 5471, Form 8992, possible section 962 election
UK sole trade or consultancy	Self Assessment; Class 2 and Class 4 NIC	Schedule C, foreign branch basket, US self-employment tax unless a certificate of coverage applies	Schedule C, Form 8858, Form 1116 (foreign branch)

Schedule B Part III: the two boxes that reveal everything

Turn to Schedule B of your Form 1040 and look at Part III — the section headed Foreign Accounts and Trusts. There are two questions there. The first asks whether you had a financial interest in, or signature authority over, a financial account located in a foreign country, and if so requires you to name the country. The second asks whether you received a distribution from, or were a grantor to or transferor to, a foreign trust.

On a properly prepared London return, the first question is answered Yes and the country is United Kingdom. If your return shows those boxes blank, or answered No while you hold a British current account, you are looking at the single most diagnostic error in expat return preparation. It tells you the preparer never ran the foreign account workflow at all. Everything downstream — FBAR, Form 8938, PFIC analysis — will be missing too.

It also matters legally. An unanswered or falsely answered Schedule B question is what the IRS points to when arguing that a failure to file an FBAR was wilful rather than non-wilful, and the penalty difference between those two characterisations is enormous. You can model the exposure with our FBAR penalty calculator.

FBAR and Form 8938: related, not interchangeable

These are two different filings, to two different agencies, with two different thresholds, and a competent return produces both where required.

• FinCEN Form 114 (FBAR) is filed electronically with FinCEN, not with your 1040. It is triggered when the aggregate maximum value of your foreign financial accounts exceeds $10,000 at any point in the year. Aggregate is the trap: five accounts of £2,000 each trigger it. It follows the return date with an automatic extension into October.
• Form 8938 is a FATCA statement filed with the 1040. For a US person living abroad the thresholds are considerably higher — broadly $200,000 at year end or $300,000 at any time for a single filer, and $400,000 or $600,000 respectively for joint filers. The IRS sets out the comparison in its summary of FATCA reporting for US taxpayers.

Form 8938 captures things the FBAR does not: unlisted shares in your own UK company, interests in foreign partnerships, certain pension interests, and — critically — it has a part where you cross-reference assets already reported on Forms 8621, 5471, 8858 and 3520. A Form 8938 with that cross-reference section empty, while you hold UK funds, is internally inconsistent with the rest of the return.

The reconciliation test: pull your FBAR schedule and your Form 8938 account listings side by side. Every depository or custodial account on the 8938 should appear on the FBAR. If they disagree, one of them is wrong.

Form 8621: your ISA, your unit trusts and your OEICs

This is where most UK-prepared returns collapse. A UK-domiciled fund — an OEIC, a unit trust, an investment trust, most London-listed ETFs — is, from the US perspective, a passive foreign investment company. The consequence is a separate Form 8621 for each fund, each year, and a punitive default regime: excess distributions and gains are thrown back across your holding period, taxed at the highest ordinary rate for each prior year, with a non-deductible interest charge layered on top.

The alternatives are elections, and they must be made properly and timely. A mark-to-market election is available where the fund's shares are regularly traded on a qualified exchange, and produces annual ordinary income or loss on the movement in value. A qualified electing fund election requires the fund to provide a PFIC annual information statement — most UK retail funds historically did not, though a growing number of platforms now supply them on request. The IRS overview sits at About Form 8621.

What "great" looks like here is not necessarily a stack of Forms 8621. It is evidence that the question was asked: a schedule listing each holding, its PFIC status, the election made or the reason none was available, and a computation. If your return shows a stocks and shares ISA on the FBAR and no Form 8621 anywhere, ask why in writing. If your ISA holds individual shares rather than funds, there may legitimately be no PFIC — but that is a conclusion, and it should have been reached deliberately. Our cross-border tax planning team routinely restructures portfolios to eliminate the problem prospectively.

Your UK pension: what should and should not appear

The UK–US double taxation convention, published by HMRC on its USA: tax treaties page, contains pension provisions that are unusually generous — and unusually misapplied.

Correctly prepared, a UK workplace pension or SIPP for a US citizen generally shows: no current US taxation of investment growth inside the wrapper; the pension reported as a specified foreign financial asset on Form 8938; the account reported on the FBAR where the taxpayer has a reportable interest; and, where a treaty position is being relied upon that requires disclosure, a Form 8833 attached. Employer contributions and the treatment of your own contributions require analysis under the treaty's pension scheme article, and the answer differs between an occupational scheme and a personal SIPP.

Two things you should not see. You should not see a UK registered pension reported as a foreign grantor trust on Forms 3520 and 3520-A as a matter of routine — that position is aggressive and, for pension schemes, largely superseded. And you should not see the 25% pension commencement lump sum treated as tax free on the US return. The treaty's lump-sum provision does not survive the saving clause for a US citizen, and the mainstream practitioner position is that the payment is taxable in the United States even though HMRC exempts it. That single mismatch has generated more surprise US liabilities among London-based Americans than any other item.

Schedule E: the London flat you let out

If you have a UK rental property, Schedule E should be present with a full statement of income and expenses in US dollars — not a translated copy of the UK property pages. The differences are material:

• Mortgage interest. The UK restricts finance costs on residential lets to a basic-rate tax reducer. The US permits a full deduction against rental income. Your US taxable rental profit will therefore usually be lower than your UK profit, which changes the foreign tax credit position and can strand UK tax.
• Depreciation. Foreign residential rental property is depreciated under the alternative depreciation system over a longer recovery period than domestic US property. Depreciation is not optional — it is recaptured on sale whether or not you claimed it. A Schedule E with no depreciation line is a defect, not a saving.
• Currency. Income and expenses should be translated at a consistent, defensible rate applied to the transactions, not a single year-end conversion of the net sterling figure.
• The mortgage itself. Repaying or remortgaging a sterling loan can generate a US foreign currency gain under section 988 if sterling has weakened since drawdown. It is taxable, it is invisible to HMRC, and almost no generalist return computes it.

Form 8858: the omission that catches consultants and sole traders

If you carry on a trade or business in the UK personally — a consultancy, a professional practice, freelance work invoiced from London — you have a foreign branch for US purposes. That means Schedule C, self-employment considerations, a foreign branch basket Form 1116, and Form 8858, the information return for foreign disregarded entities and foreign branches. The same applies if you own a UK limited company for which a check-the-box election has been made to treat it as disregarded.

Form 8858 is an information return. Its omission carries fixed penalties and, more importantly, can leave the statute of limitations open on your entire return. It is one of the most commonly missing forms we see when reviewing work prepared by UK-only firms, because it has no UK analogue at all.

Form 5471 and GILTI: if you own a UK limited company

Founders and consultants operating through a UK Ltd need Form 5471 with the correct category of filer and the correct schedules — not a token first page. Beyond the information return, the substantive issue is that a controlled foreign corporation's active profits can be pulled into your personal US income as global intangible low-taxed income before you take a penny of dividend, computed on Form 8992. Whether a section 962 election is worth making, and how UK corporation tax interacts with the credit mechanics, is a genuine modelling exercise. If your return shows a UK company on Form 8938 but no Form 5471, something has gone badly wrong. This is core territory for our high net worth practice.

The 3.8% charge your UK tax cannot offset

Net investment income tax is levied at 3.8% on investment income above modified adjusted gross income thresholds. Here is the point almost no generalist guide makes: foreign tax credits claimed under section 901 cannot be applied against it, and the prevailing view is that the US–UK treaty does not provide relief either. A London-based American with substantial UK investment income can therefore owe real US tax on income already fully taxed in the UK at dividend or additional rates. A good preparer sees this coming and positions the portfolio in advance; a weak one discovers it in April. It should be computed on Form 8960, and that form should be in your return if your investment income is meaningful.

Does your 1040 agree with your Self Assessment?

The two returns are prepared under different calendars, different residence rules and different characterisations, but they describe the same person. A cross-border preparer should be able to walk you from one to the other. Watch for these mismatch points:

• Timing. UK 6 April to 5 April against US 1 January to 31 December. A March bonus lands in different years in the two systems, which is exactly how income gets double taxed or accidentally omitted.
• Deadlines. US expatriates get an automatic extension to 15 June, extendable to 15 October; UK Self Assessment is due 31 January. Your US preparer often cannot finalise foreign tax credits until the UK position is settled, which is why both returns should be handled together by US–UK tax accountants rather than by two firms who never speak.
• Foreign income reporting to HMRC. If you are UK resident and taxed on the arising basis, HMRC expects your worldwide income; its guidance on tax on foreign income is the starting point. US-source income omitted from Self Assessment is as much a problem as UK income omitted from the 1040 — and HMRC nudge letters based on exchanged financial data are now routine.
• Making Tax Digital. HMRC's phased Making Tax Digital for Income Tax regime brings qualifying self-employment and property income into quarterly digital reporting from April 2026. If you have a UK let or a sole trade, this changes your UK record-keeping, and by extension the evidence base underpinning your Schedule E and Schedule C.

A twenty-minute audit of last year's return

Open the PDF and work down this list. Anything you answer "no" or "not sure" to belongs on a list for your adviser.

• Is Schedule B Part III answered Yes, with United Kingdom named?
• Is there a Form 1116 for each relevant income category, plus the carryover reconciliation schedule?
• If there is a Form 2555, was the decision to use it documented — and were excess credits deliberately forgone?
• Is Form 8938 present, and does it cross-reference your other international forms?
• Do the accounts on Form 8938 reconcile to your FBAR?
• Is every UK fund, ISA holding, OEIC or investment trust either on a Form 8621 or explained in a schedule?
• Is your pension on Form 8938, and is any treaty position disclosed on Form 8833?
• Does Schedule E show depreciation, full mortgage interest and transaction-level currency translation?
• If you trade personally in the UK, is Form 8858 attached?
• If you own a UK company, is there a complete Form 5471 with the right filer category — and was GILTI considered?
• Was net investment income tax computed on Form 8960?
• Is there a paid preparer signature and PTIN — or was a cross-border return effectively self-prepared?

What to do if the audit fails

Most people who work through that list find at least one gap. The remedy depends on scale. A single omitted Form 8621 or a mis-built Form 1116 is usually a matter for an amended return on Form 1040-X, filed with a clear statement of what changed. Missing FBARs alone, with no unreported income, are generally handled through the delinquent submission procedures. Where several years are wrong, income was under-reported, and the failure was non-wilful, the IRS Streamlined Foreign Offshore Procedures remain the cleanest route back — no penalty, three years of amended returns, six years of FBARs and a sworn non-wilfulness certification. Our IRS streamlined filing experts handle exactly this work, and the sequencing matters enormously: once the IRS or a bank has made contact, eligibility can close.

What we would urge you not to do is quietly file a better return next year and hope the earlier ones age out. International information return failures do not start the assessment clock. They hold it open, indefinitely, on the whole return.

The standard you should be buying

Excellent expat return preparation is not a commodity and is not priced like one. It looks like a preparer who asks for your P60, your P11D, your Self Assessment calculation, your pension statements, your platform's fund-level holdings report and your mortgage statements before quoting. It looks like a written summary of the elections made and why. It looks like carryover schedules that persist year to year. And it looks like a return whose US and UK sides can be reconciled on a single page. If you would like the wider context, our guides library covers the surrounding compliance landscape in the same detail.

If last year's return does not meet that description, the exposure is not theoretical — it is sitting in an open assessment window. Send us the PDF and we will tell you, plainly, what is missing and what it will take to put right. To arrange a confidential, no-obligation review of your prior-year filings, contact our cross-border team and ask for a return diagnostic. Everything you share is handled in confidence and reviewed by a preparer who works in both systems every day.