Missed US Tax Returns: Step-by-Step Guide for Londoners

If you are an American in London with Missed US tax returns, the route back is ordered, not chaotic. You establish which years are genuinely open, choose a disclosure route, rebuild UK payroll and investment records onto a US calendar year, then lodge the completed pack in the correct sequence. Most non-willful filers end up penalty-free.

What follows is the workflow Jungle Tax uses for London-based clients who arrive with anything from two to twenty unfiled years. It is deliberately chronological: each step produces the raw material the next step consumes. Attempting the steps out of order — filing an FBAR before you know which years you are disclosing, or preparing a Form 1040 before you have converted UK payroll to a calendar-year basis — is the single most common reason a catch-up has to be redone.

What actually counts as a missed US tax return?

US federal income tax follows citizenship, not residence. A US citizen or green card holder resident in the United Kingdom files a Form 1040 reporting worldwide income every year the gross-income threshold is met, regardless of how much UK tax has already been deducted at source through PAYE or settled through Self Assessment. Paying HMRC in full does not discharge the US filing obligation; it usually only removes the US liability, via foreign tax credits, once a return is actually filed.

That distinction matters because a very large share of London-based non-filers owe nothing. UK effective rates on employment income typically exceed US rates at the same income level, so the arithmetic frequently produces a nil balance. The exposure is not the tax. It is the unfiled information returns — FBAR, Form 8938, Form 5471 for a UK limited company, Form 3520 for certain trusts — where penalties are assessed per form, per year, irrespective of whether any tax was due.

Step 1: Establish which years are genuinely open

Before you prepare anything, fix the perimeter. The assessment statute of limitations only begins to run when a return is filed. For a year in which no return was ever filed, the period remains open indefinitely — there is no point at which an unfiled 2011 return becomes safe by the passage of time.

How far back does the IRS look?

• No return filed: the limitations period never starts. The year stays technically open.
• Return filed, ordinary case: generally three years from filing.
• Substantial omission: generally six years where gross income omitted exceeds 25% of that reported, and a separate six-year rule applies where more than $5,000 of foreign income was omitted.
• Missing information returns: where a required international information return (such as Form 8938, 5471 or 3520) was not filed, the limitations period for the entire return can remain open until three years after that form is eventually filed.

In practice, the disclosure programme you use then defines a far shorter working perimeter. The Streamlined Foreign Offshore Procedures require the most recent three years of delinquent or amended income tax returns for which the due date has passed, and the most recent six years of FBARs. That asymmetry — three years of returns, six years of FBARs — is not a drafting error, and getting it wrong in either direction causes rejection or unnecessary work.

Which three years are “the most recent three”?

The three years are measured by original due date, including extensions actually obtained. For a London filer this frequently shifts the window, because Americans abroad receive an automatic extension to mid-June and can extend further to mid-October. Deciding the perimeter on 1 September produces a different three-year set than deciding it on 1 May. Fixing this date first, and documenting it, prevents the awkward position of a return being prepared for a year that has just dropped out of the window.

Step 2: Choose the correct route back into compliance

There are several formal paths, and the choice is driven almost entirely by one question: was the failure to file non-willful? Non-willful means negligence, inadvertence, mistake, or a good-faith misunderstanding of the law. It is a factual determination you certify under penalty of perjury, and it is where professional judgement earns its fee.

Route	When it fits	Years required	Penalty exposure
Streamlined Foreign Offshore Procedures	Non-willful, meets the non-residency test, no IRS examination already open	3 years of returns; 6 years of FBARs; Form 14653 certification	Miscellaneous offshore penalty waived for qualifying non-residents
Delinquent FBAR submission procedures	Income was correctly reported and tax paid; only FBARs were missed	FBARs only	No penalty where there is a reasonable cause statement and no unreported income
Delinquent international information return procedures	Returns filed, but Form 5471, 8938 or 3520 omitted	The missing forms, with reasonable cause	Depends on the strength of the reasonable cause statement
IRS Criminal Investigation Voluntary Disclosure Practice	Conduct that may be willful	Typically six years	Substantial, but protective against criminal referral

Two disqualifiers end the streamlined option immediately: the IRS has already initiated a civil examination for any year, or you are under criminal investigation. If either applies, stop and take advice before filing anything. The full eligibility conditions are set out in the IRS's own procedures for US taxpayers residing outside the United States, and our IRS streamlined filing team assesses eligibility before any document is drafted.

The non-residency test for a London filer

A US citizen or green card holder must, in at least one of the three most recent years, have had no US abode and have been physically outside the United States for at least 330 full days. Most established London residents clear this comfortably. The people who do not are those who moved mid-period, kept a US home available, or travel heavily on business. Reconstruct the day count from passport stamps, airline records and calendar entries before certifying — a failed 330-day count discovered later is a costly correction.

Step 3: Reconstruct the UK record set

This is the step generic expat guides skip, and it is where the actual work sits. You cannot prepare a US return from UK memory; you need documentary support that reconciles to something HMRC also holds.

What to pull, and from where

• HMRC personal tax account: pay and tax history by employment, usually going back several years. This is the fastest way to recover figures for jobs you have long since left.
• Forms P60 and P45: the year-end and leaver summaries of gross pay and PAYE deducted for each UK tax year.
• Form P11D: benefits in kind — private medical cover, company car, interest-free loans. These are UK-taxable benefits that are also US-taxable compensation and are routinely omitted.
• SA302 and Self Assessment calculations: where you filed a return for rental income, dividends, or because of the high income child benefit charge.
• Monthly payslips: essential, because year-end forms are annual and you need to allocate pay across two UK tax years to build a calendar year.
• Employer pension and share scheme statements: contribution histories, and grant, vest and exercise records for options, RSUs, SAYE and share incentive plans.
• Bank and building society statements: for every account, including dormant ones, with maximum balances by year for FBAR purposes.
• Broker and platform consolidated tax certificates: UK investment platforms issue annual summaries showing dividends, interest and disposals.
• ISA statements: in full. An ISA is a UK wrapper with no US recognition, and its contents must be examined line by line.

Where records are genuinely lost, reconstruction is still possible: bank statements evidence net pay, from which gross pay and PAYE can be modelled using the coding notices and rates for the year. Document the method. A reasoned, disclosed estimate is defensible; a silent guess is not.

Step 4: Convert a UK tax year into a US calendar year

The UK tax year runs 6 April to 5 April. The US tax year is the calendar year. Nothing in either system reconciles automatically, and every figure on the US return must be recut onto the calendar basis.

Feature	United States (IRS)	United Kingdom (HMRC)
Tax year	1 January to 31 December	6 April to 5 April
Basis of taxation	Citizenship and residence; worldwide income	Residence, with the post-April 2025 four-year foreign income and gains regime for new arrivals
Standard filing deadline	15 April, automatic extension to 15 June for those abroad, further extension available to 15 October	31 January online, for the year ended the previous 5 April
Foreign account reporting	FBAR (FinCEN Form 114) where aggregate balances exceed $10,000; Form 8938 at higher thresholds	No standalone account report; foreign income declared on the Self Assessment foreign pages
Formal catch-up route	Streamlined Filing Compliance Procedures	Worldwide Disclosure Facility / Digital Disclosure Service
Look-back on disclosure	3 years of returns, 6 years of FBARs	Typically 4, 6 or up to 20 years depending on behaviour

How do you allocate UK payroll to a US calendar year?

Take the monthly payslips for the two UK tax years that overlap the US calendar year. For calendar 2024, that is the periods running April 2023 to April 2024 and April 2024 to April 2025. Sum the January to December pay periods on the date the pay was actually received, because the US measures cash-basis compensation by receipt. Do the same for PAYE and employee National Insurance withheld. Bonus timing matters disproportionately: a March bonus sits in one calendar year and one UK year, but a bonus paid in early April crosses both boundaries at once.

The same exercise applies to UK tax paid for foreign tax credit purposes. Under the accrued method, UK tax is allocated to the year the underlying income arose; under the paid method, to the year of payment. Balancing payments and payments on account made in January and July have to be traced back to the UK year they relate to. Getting this allocation wrong is the most frequent cause of an understated foreign tax credit and an entirely avoidable US balance due.

Step 5: Currency conversion that will survive review

US returns are prepared in US dollars. For most recurring items you may use the annual average exchange rate for the year. For discrete transactions — a share disposal, a pension lump sum, a property sale — the spot rate on the transaction date generally gives the more accurate and more defensible result, and for capital gains you need separate rates for acquisition and disposal, which is precisely how a sterling-flat property sale can generate a US dollar gain. FBAR maximum balances use the year-end Treasury reporting rate. Pick a method per category, apply it consistently across all years in the pack, and keep the rate table with the working papers.

Step 6: The UK holdings that complicate a London filer's return

ISAs and UK funds

A stocks and shares ISA receives no US recognition. Income and gains inside it are currently taxable in the US. Worse, most UK-domiciled collective investments — OEICs, unit trusts, investment trusts and UK-listed ETFs — meet the definition of a passive foreign investment company. PFIC holdings require a Form 8621 per fund per year and, absent an election, are taxed under a punitive excess-distribution regime with an interest charge. A portfolio of a dozen UK funds can turn a straightforward catch-up into a substantial engagement, and the analysis has to be done before the returns are drafted, not after.

UK pensions

The US-UK double tax treaty gives useful protection for UK pension arrangements, generally allowing tax deferral on growth inside a pension and coordinating the treatment of contributions and distributions. The protection is not automatic in every case, and the position for SIPPs, employer occupational schemes and drawdown differs. Where treaty positions are taken on a late return, they are disclosed rather than assumed. Foreign pension arrangements can also trigger reporting on Form 8938 and, in some structures, the Form 3520 series.

UK property, share schemes and company interests

London rental property requires a US Schedule E computed on US rules — 40-year straight-line depreciation for foreign residential property, not the UK cash-basis figures, and a mortgage interest position that differs sharply from the UK's restricted relief. UK share schemes vest and are taxed on different timelines in each country, creating credit mismatches. And a personal service company — extremely common among London consultants and founders — is a controlled foreign corporation requiring Form 5471, potentially with Subpart F or global intangible low-taxed income inclusions. This is the point at which a catch-up stops being a compliance exercise and becomes cross-border tax planning.

Step 7: Choose the exclusion or the credit, deliberately

Two mechanisms prevent double taxation. The foreign earned income exclusion removes a capped amount of foreign earned income, indexed annually. The foreign tax credit on Form 1116 credits UK tax paid against the US liability on the same category of income.

For a London filer paying UK rates, the credit is usually the stronger choice. It covers investment income as well as earnings, it generates carryforward credits that can shelter future US liabilities, and it preserves eligibility for the refundable portion of the child tax credit, which the exclusion can forfeit. The exclusion suits lower-taxed or self-employed situations, and requires an affirmative election. On a delinquent return, the timing rules around making that election for the first time are strict, which is another reason the choice is made before the first return is drafted rather than year by year. Once elected and later revoked, the exclusion cannot generally be re-elected for five years without consent.

Step 8: Rebuild the information returns

Six years of FBARs sit alongside three years of returns. An FBAR is required where the aggregate maximum value of foreign financial accounts exceeded $10,000 at any point in the year — aggregate, not per account, so five accounts of three thousand pounds each trigger it. Include current accounts, savings, ISAs, brokerage accounts, certain pensions and any account over which you hold signature authority, including a UK employer's account or a family member's account you help manage. Our FBAR penalty calculator illustrates the exposure that a qualifying streamlined submission removes; the filing mechanics are described on the IRS FBAR guidance page.

Form 8938 operates on higher thresholds for taxpayers living abroad and attaches to the Form 1040 itself. It overlaps with the FBAR but is not the same list: it captures assets an FBAR does not, and both are filed where both apply.

Step 9: Assemble and lodge the pack in the correct order

Sequence matters, because the certification is a statement about work already completed.

• First, finalise all three income tax returns and every attached information return, so the figures are locked.
• Second, e-file the six years of delinquent FBARs through the FinCEN BSA system, selecting the reason for late filing that corresponds to the streamlined procedures. Retain the acknowledgements.
• Third, draft Form 14653. The narrative is the heart of the submission: specific, chronological, and personal — when you left the US, what you were told and by whom, when and how you discovered the obligation, and what you did next. Generic language invites follow-up questions.
• Fourth, mark the returns and the certification as the procedures require and submit the paper package to the designated IRS address for streamlined submissions. These returns are not e-filed as part of the package.
• Fifth, pay any tax and interest due with the submission. Failure-to-file and failure-to-pay penalties are waived under the programme; statutory interest is not.
• Sixth, file the current year on time, by the normal route. A streamlined submission that is immediately followed by another missed year undermines the non-willful narrative entirely.

Keep a complete duplicate of everything submitted, including the certification and the FBAR acknowledgements. There is no acceptance letter; the IRS does not confirm that a streamlined submission has been approved, and your file is your only evidence of what was disclosed and when.

Does HMRC need a disclosure as well?

Frequently, yes — and it is the question generalist US expat guides ignore. An American in London who under-reported to the IRS has often also under-reported to HMRC: US-source dividends, a US brokerage account, a 401(k) distribution, or US rental income that belonged on the foreign pages of a Self Assessment return. HMRC's guidance on tax on foreign income sets out the obligation, and the Worldwide Disclosure Facility is the corresponding UK route.

HMRC assessment windows run to four years for innocent error, six years for careless behaviour and up to twenty years for deliberate conduct, with an enhanced regime for offshore matters. The two disclosures should be planned together: figures must be consistent across both, and a foreign tax credit claimed on one side has to match what was actually paid on the other. Running them independently produces contradictions that neither authority overlooks. Our US-UK tax accountants prepare both sides from one reconciled data set.

What happens after the pack is lodged?

Processing of a paper streamlined submission commonly takes several months and can run beyond a year. Silence is the normal outcome and is not a cause for concern. Refunds arising from over-withheld US tax on a delinquent return are subject to their own claim deadlines, which is one reason not to delay. If the IRS does correspond, it is usually a request for clarification on the certification narrative or a specific figure, and a well-documented file answers it in a single letter.

What are the mistakes that cost the most?

• Filing three years quietly and hoping, rather than using the formal programme — this forfeits the penalty waiver and can look evasive.
• Filing the FBARs before the returns are finalised, then discovering an account that changes the disclosure.
• Using UK tax year figures directly on a US return without the calendar-year recut.
• Ignoring ISAs and UK funds, then facing a PFIC correction later.
• A vague Form 14653 narrative that fails to explain how and when the obligation was discovered.
• Forgetting state filing obligations, where a former state of residence still asserts a claim.
• Missing the current year while the historic pack is in preparation.

Speak to us in confidence

Missed US tax returns are a solvable, finite problem when they are worked in the right order — and for most London-based Americans the eventual tax cost is far smaller than the anxiety that preceded it. If you have unfiled years, undisclosed UK accounts, an ISA or fund portfolio, or a personal company that has never appeared on a US return, contact our cross-border team for a confidential discussion. We will scope the perimeter, confirm the right route, and handle both the IRS and HMRC sides from a single reconciled file. Further reading is available across our cross-border guides.