When is my US tax return due if I live in the UK?

For a calendar-year filer the regular due date is April 15. If your tax home is abroad you get an automatic two-month extension to June 15, and you can extend further to October 15 by filing Form 4868 with the out-of-country box on line 8 checked. Where a due date falls on a Saturday, Sunday or legal holiday it moves to the next business day, so diary the rule rather than a fixed date.

Does the June 15 extension also give me longer to pay?

No. Every extension available to a US person abroad is an extension of time to file, not to pay. IRS Publication 54 is explicit that interest is due on any tax not paid by the regular due date of the return, which for a calendar-year filer is April 15. In practice this means paying a close estimate by April 15 and then using the extension period to complete the investment reporting properly.

Do I have to request the FBAR extension to October 15?

No. The IRS confirms that if you fail to meet the FBAR annual due date of April 15 you are allowed an automatic extension to October 15, and that you do not need to request it. The FBAR is filed electronically through FinCEN's BSA E-Filing System, separately from your federal return. Because it needs only calendar-year account balances and no UK documents, we usually file it in the first quarter instead.

Why can't my US return be finished in March if my UK income is simple?

Because the UK documents do not have to exist yet. Your employer is not required to give you a P60 until 31 May, P11D benefits information is not due until 6 July, and a pension savings statement can arrive as late as 6 October. UK investment statements are produced on a 5 April cycle with no fixed deadline. Any US return finalised in March for a UK-employed investor is built on estimates.

Do I need to file Form 3520 for a gift from my UK parents?

You do if the aggregate received from that nonresident alien individual or foreign estate exceeds 100,000 US dollars during the taxable year, and each gift over 5,000 US dollars must then be separately identified. Gifts from foreign corporations or partnerships have a much lower inflation-adjusted threshold. Form 3520 is generally due April 15, is extended by Form 4868, but can never run beyond October 15 for a calendar-year taxpayer.

How do UK payments on account interact with US estimated tax?

They are separate obligations on separate calendars. HMRC takes a balancing payment and first payment on account on 31 January and a second payment on account on 31 July, while the four US estimated dates are April 15, June 15, September 15 and January 15. The UK payment dates matter to the US position because they determine when foreign tax is actually paid, and therefore when a foreign tax credit becomes available.

US Personal Tax Services: UK Investor Tax Calendar

US personal tax services for a US person living in the UK with a substantial investment portfolio are built around a twelve-month calendar, not a single April deadline, because the income tax return is only one of six or seven filings that can fall due in a year. Form 1040 is due on April 15 for a calendar-year filer, with an automatic two-month extension to June 15 where your tax home is abroad, and a further extension to October 15 on Form 4868. FinCEN Form 114, the FBAR, is due on April 15 with an automatic extension to October 15 that requires no request at all. Form 8938, Form 8621, Form 5471, Form 8865 and Form 8858 travel with the income tax return and inherit its extended due date. Form 3520 runs on its own timetable. Estimated tax payments fall on four separate dates that no filing extension moves.

That is the deadline map, and it is the part every competing article publishes. The part almost nobody publishes is the part that actually governs whether the year goes smoothly: the order in which the work can be done at all. A US calendar year ends on 31 December, but the UK documents that supply the numbers are produced on a 5 April cycle and are not legally required to exist until 31 May, 6 July or 6 October. In the returns we prepare, the binding constraint is almost never the IRS deadline. It is the arrival date of a UK document. This article sets out the calendar in the order the work becomes possible, and gives you a triage you can run once a year against your own holdings. Throughout, US federal dates are written in US form (April 15, June 15) and UK dates in UK form (31 January, 5 April), because mixing the two is the single most common source of diary errors we see in cross-border files.

Why US Personal Tax Services for UK Investors Run on a Calendar, Not a Deadline

A US person in the UK holding a diversified portfolio is not filing one return to one authority. They are filing to the IRS, to FinCEN through a separate electronic system, and to HMRC, across two different tax years, in two currencies, with three different definitions of what counts as a reportable asset. The IRS confirms at irs.gov/individuals/international-taxpayers/us-citizens-and-resident-aliens-abroad that the regular due date is April 15 and the automatic extended due date for a citizen or resident alien residing overseas is June 15, and that where a due date falls on a Saturday, Sunday or legal holiday it is delayed until the next business day. That weekend rule matters more than it sounds: it means you should diary the rule, not a specific future date, because April 15 and June 15 shift in some years and a hard-coded date in a calendar app will eventually be wrong.

The second reason a calendar beats a deadline list is that extensions of time to file are not extensions of time to pay. IRS Publication 54, at irs.gov/publications/p54, is explicit that even where an extension is allowed, interest is due on any tax not paid by the regular due date of the return. So the practical year has two separate spines running through it: a payment spine that is fixed to April 15 and to the four estimated tax dates, and a filing spine that can be stretched to June 15, then October 15, and in limited circumstances to December 15. Treating those as one thing is how a well-organised investor ends up paying interest on a return that was filed perfectly on time.

Which of These Forms Actually Apply to Me? The Annual Triage

Run this once a year, ideally in January, against your actual holdings rather than against last year's return. The failure mode we see most often is a client who assumes the form set is stable because it was stable for three years, then acquires one new holding that pulls in an entirely new information return. Work through each line and answer yes or no.

Did the combined maximum balance of every foreign financial account you own or can sign on exceed 10,000 US dollars at any point in the calendar year? If yes, an FBAR is required. The IRS states the test as the aggregate value exceeding 10,000 US dollars at any time during the calendar year reported, which means a single day of a property completion sitting in a current account can trigger it.
Did your specified foreign financial assets exceed 200,000 US dollars on the last day of the tax year or 300,000 US dollars at any time during the year, if you are unmarried or married filing separately and living abroad? For married filing jointly abroad the figures are 400,000 and 600,000 US dollars. If yes, Form 8938 is required with your return. The thresholds are published at irs.gov/businesses/corporations/summary-of-fatca-reporting-for-us-taxpayers.
Do you hold any UK or non-US pooled fund: an OEIC, unit trust, investment trust, offshore fund or non-US ETF? If yes, you are almost certainly a shareholder in one or more passive foreign investment companies and Form 8621 is in scope.
Did you receive a distribution from, or dispose of any part of, a non-US fund holding during the year? If yes, Form 8621 is required for that fund regardless of size.
Do you own shares in a UK limited company, including your own trading or investment company or a founder stake? If yes, test yourself against the Form 5471 filer categories.
Are you an officer or director of a UK company in which US persons hold a significant stake? That can create a Form 5471 obligation even where your own shareholding is modest.
Do you hold an interest in a UK LLP, a general partnership, or a fund structured as a partnership? If yes, Form 8865 is in scope.
Do you operate through a UK entity that is disregarded for US purposes, or run a UK branch of a US business? If yes, Form 8858 is in scope.
Did you receive gifts or bequests from non-US individuals aggregating more than 100,000 US dollars during the year, or from foreign corporations or partnerships above the inflation-adjusted threshold? If yes, Form 3520 Part IV is in scope.
Is any material part of your income not subject to US withholding, which for a UK-resident investor is usually all of it? If yes, estimated tax payments are in scope and the four dates apply to you.

The triage above catches the position as at 31 December. What it does not catch, and what causes most of the late filings we are asked to remediate, is the obligation that switched on partway through the year and switched off again before anyone looked. These mid-year triggers are worth a diary entry of their own, because none of them will appear on a year-end statement.

Opening any new UK account, including a savings account opened to hold sale proceeds for six weeks. FBAR aggregation is tested on the maximum balance at any time, not the balance on 31 December, so an account closed in August still counts.
A single large credit passing through an account: a bonus, a property completion, an option exercise or a business sale. It can push aggregate balances past the FBAR threshold or past the any-time-during-the-year Form 8938 threshold even though the year-end position looks unremarkable.
Receiving your first distribution from a fund you have held quietly for years. The distribution itself creates a Form 8621 filing obligation for that fund for that year.
Crossing an ownership or voting threshold in a UK company, whether by your own subscription or by someone else's shares being redeemed around you. Dilution and redemption change your percentage without you doing anything.
Being appointed a director of a UK company, which can bring a Form 5471 category into play on the appointment date.
Receiving a large gift from a non-US family member. The Form 3520 threshold is tested on aggregate amounts received during the taxable year, so several transfers can combine into a filing.
Acquiring signature authority over an account you do not own, such as an elderly relative's account or a company account. Signature authority alone can create an FBAR obligation.

The Dependency Map: Which UK Documents Gate Which US Forms

This is the section that changes how the year is run. A US form cannot be completed until the underlying UK document exists, and UK documents have their own statutory production dates that sit inconveniently across the US filing season. Here are the ones that matter, with the dates HMRC actually imposes.

P60: your employer must give it to you by 31 May following the end of the UK tax year, per gov.uk/paye-forms-p45-p60-p11d/p60. It reports 6 April to 5 April, so it never maps cleanly onto a US calendar year and always needs to be combined with payslips and the prior year P60 to rebuild a January to December figure.
P11D and P11D(b): due to HMRC and to you by 6 July, with Class 1A National Insurance payable by 22 July electronically or 19 July by cheque, per gov.uk/employer-reporting-expenses-benefits/deadlines. Until the P11D exists you cannot finalise the value of UK benefits in kind for US purposes.
Consolidated tax vouchers and annual investment statements from UK brokers and platforms: these are produced after 5 April on a UK tax year basis. There is no statutory deadline comparable to the US Form 1099 cycle, and in practice they arrive between late April and July.
Pension savings statements: a scheme administrator must provide one by 6 October following the end of the tax year where your pension input amount exceeded the annual allowance. That is the latest of all the major UK documents and it lands only nine days before the US October 15 extended deadline.
Fund-level PFIC information: annual reports, distribution data and any PFIC annual information statement from the fund manager. These have no fixed date at all, they are the hardest single item to obtain for UK-domiciled funds, and their absence is the most common reason a return sits unfinished in September.
Your own 31 December account balances and maximum balances, in the account currency. These exist on 1 January and are the only major input available immediately.

Read those dates against the US deadlines and the ordering problem becomes obvious. The earliest realistic start date for each US form is therefore not January for everything. It is roughly as follows, and building the year in this order rather than in deadline order is what stops the file stalling.

FBAR (FinCEN Form 114): can be started on 2 January. It needs only calendar-year account balances and maximum values, no UK document, and no income analysis. It is the one filing that can be finished before any UK paperwork arrives, and finishing it early removes an April 15 item from the diary permanently.
Estimated tax for the Q4 payment due January 15: can be finalised in early January using the prior year safe harbour, which needs only last year's completed return.
Form 8938: can be substantially drafted in January from year-end and any-time-during-the-year account values, but the income columns cannot be finalised until investment statements arrive, so realistically it completes from May onwards.
Form 1040 employment income: not reliably completable before late May or early June, because the P60 does not have to exist until 31 May and benefits data does not have to exist until 6 July. Anyone promising a finished return in March for a UK-employed client is estimating.
Form 8621 for PFICs: earliest realistic start is when fund distribution data arrives, typically May to July. Where a qualified electing fund statement is needed and the manager does not routinely issue one, assume months, not weeks, and start chasing in January.
Form 5471, 8865 and 8858: gated by the UK entity's own accounting cycle. If the UK company has a 31 March or 5 April year end, the US information return depends on management accounts that may not be finalised until the autumn.
Form 3520 for foreign gifts: can be prepared as soon as the transfers are documented, which is usually immediately, and it is due April 15 with extension available to October 15 at the latest.
Pension annual allowance interaction: cannot be finalised before 6 October in a year where a pension savings statement is required, which is a strong argument for extending to October 15 as a default rather than as a fallback.

January to March: Open the File Before the UK Data Exists

The Q4 estimated tax payment for the prior year falls on January 15. Immediately after it, three things should happen: pull every 31 December and maximum-balance figure for every account, run the annual triage above, and issue the first chase for PFIC information from every fund manager. The FBAR can then be prepared and filed in January or February through FinCEN's BSA E-Filing System at bsaefiling.fincen.gov. The IRS confirms at irs.gov/businesses/small-businesses-self-employed/report-of-foreign-bank-and-financial-accounts-fbar that the FBAR is filed electronically through that system and is not filed with your federal tax return, that its annual due date is April 15, and that an automatic extension to October 15 applies without any request. Filing it in February rather than relying on that extension is free and it takes a penalty-bearing item off the board.

The other January task is the currency decision. The IRS states at irs.gov/individuals/international-taxpayers/yearly-average-currency-exchange-rates that it has no official exchange rate, that it generally accepts any posted exchange rate used consistently, and that in general you use the spot rate prevailing when you receive, pay or accrue the item. Decide once, at the start of the year, which convention you are applying to which class of item, document it, and apply it across the 1040, Form 8938 and the FBAR. Inconsistency between those three filings is a reconciliation question waiting to be asked, and it is entirely avoidable.

April: The Hinge Month for Form 1040, the FBAR and Form 3520

April 15 is the payment date. It is the date any balance for the prior year must actually be paid to avoid interest, the date the first estimated payment for the current year falls due, the nominal FBAR date, and the nominal Form 3520 date. For a US person living in the UK it is generally not the filing date, because the automatic two-month extension to June 15 applies where your tax home is abroad. Publication 54 makes clear that to use that automatic extension you must attach a statement to your income tax return explaining which situation qualified you for it. That statement is routinely omitted, and omitting it is how an automatic extension quietly stops being automatic.

April is therefore a payment and projection month rather than a filing month. The work is to estimate the prior year liability closely enough to pay it, using whatever UK data exists, and to set the current year estimated payment. The IRS sets out the Form 3520 position at irs.gov/businesses/gifts-from-foreign-person: it is due on the 15th day of the fourth month following the end of your income tax year, generally April 15 for individuals; filing Form 4868 automatically extends Form 3520; and the extension cannot run beyond the 15th day of the 10th month, October 15 for calendar-year taxpayers, even where a discretionary further extension is granted for the income tax return. That last point is a genuine trap for anyone who extends the 1040 to December 15 and assumes the whole file moves with it. It does not.

May to July: UK Documents Land and June 15 Arrives

This is when the file becomes workable. The P60 must exist by 31 May. Investment statements arrive. On 6 July the P11D lands and the benefits picture closes. In between sits June 15, which is both the automatic extended filing date for taxpayers abroad and the second estimated tax payment date. In most substantial investment cases we do not file on June 15. We file Form 4868 by June 15, with the out-of-country box on line 8 checked as Publication 54 directs, to take the deadline to October 15, and we use the intervening months to complete the PFIC and entity work properly rather than filing a return we know will need amending.

There is a separate extension that is often confused with Form 4868. Form 2350 is the Application for Extension of Time to File US Income Tax Return, and it exists for one narrow purpose: US citizens and resident aliens abroad who expect to claim the foreign earned income or housing exclusion and need more time to meet the bona fide residence or physical presence test. Publication 54 explains that it is generally granted for 30 days beyond the date on which you can reasonably expect to qualify, and that it must be filed by the due date for filing your return. For a UK-resident investor whose income is largely investment income rather than earned income, Form 2350 is usually irrelevant. For a recent arrival still counting days toward a residence test, it is the right form and Form 4868 is not.

On the UK side, 31 July is the second payment on account. GOV.UK confirms at gov.uk/self-assessment-tax-returns/deadlines that there is a second payment deadline of 31 July for payments on account, alongside the 31 January balancing payment and online filing deadline and the 31 October paper filing deadline. That 31 July payment is a UK cash outflow with no US filing consequence in the same month, which is precisely why it gets forgotten in cross-border households running a single diary.

August to October: The Extension Window Where the Real Work Happens

September 15 is the third estimated tax date. October 6 is the latest date a pension savings statement has to be issued. October 15 is the extended filing date for Form 1040, the automatic extended date for the FBAR if it was not filed earlier, the final possible date for Form 3520, and the deadline to post a letter requesting the discretionary further extension. Everything converges. This is the window in which PFIC computations are finalised and elections are made or not made, and it is the window in which Form 5471, Form 8865 and Form 8858 are completed once UK entity accounts are available.

Form 8621 deserves particular attention here because the elections are time-sensitive and effectively one-way. The IRS explains at irs.gov/forms-pubs/about-form-8621 that a US person who is a shareholder of a PFIC files the form if they receive certain direct or indirect distributions, recognise gain on a direct or indirect disposition of PFIC stock, report information regarding a qualified electing fund or section 1296 mark-to-market election, make an election reportable in Part II, or are required to file an annual report under section 1298(f), and that the form is submitted with the return by the due date including extensions. A limited exception from the annual reporting requirement exists for very small aggregate PFIC holdings, but it is set at a level a substantial portfolio passes easily and it does not help at all in a year with a distribution or a disposal. The practical point is that the election decision has to be made before the return is filed, and it cannot be made without fund data you may have been chasing since January.

November and December: The December 15 Letter and Year-End Positioning

Publication 54 confirms that taxpayers who are out of the country can request a discretionary additional two-month extension to file, to December 15 for calendar-year taxpayers, by sending the IRS a letter explaining the reasons why the additional time is needed, sent by the extended due date of October 15. It is discretionary, not automatic, it does not extend the payment date, and it does not carry Form 3520 with it. We use it where UK entity accounts or fund data genuinely have not arrived, not as a scheduling convenience. December is otherwise the month for positioning: reviewing which accounts will be open at 31 December, whether any disposal should sit in this calendar year or the next for US purposes and this UK tax year or the next for HMRC purposes, and making sure nothing is being done in the last fortnight of December that creates a new information return nobody has budgeted time for.

Estimated Tax: Four Dates That No Filing Extension Moves

The IRS sets out at irs.gov/faqs/estimated-tax/individuals/individuals-2 that the four estimated tax periods for calendar-year individuals carry due dates of April 15, June 15, September 15 and January 15 of the following year, and that where a due date falls on a Saturday, Sunday or legal holiday the payment is on time if made on the next day that is not a weekend or holiday. For a UK-resident investor these dates matter far more than they do for a US-resident employee, because almost nothing in a UK portfolio is subject to US withholding. Dividends from UK companies, gains on UK holdings, rental profits and partnership distributions all arrive gross of US tax.

The safe harbour position published at irs.gov/businesses/small-businesses-self-employed/estimated-taxes is that most taxpayers avoid the underpayment penalty if they owe less than 1,000 US dollars after subtracting withholdings and credits, or if they paid at least 90 percent of the tax for the current year or 100 percent of the tax shown on the prior year return, whichever is smaller, with special rules for higher-income taxpayers set out in Publication 505. For an investor whose income is lumpy, the prior year safe harbour is usually the sane choice, because it is a known number in January rather than a forecast of a year that has not happened yet.

Where the UK Calendar Collides With the US One

The two systems do not merely run on different dates. They run on different years, which means the same economic event is reported in different periods on each side and the foreign tax credit position has to be tracked across that mismatch. These are the collisions we plan around every year.

The 5 April UK year end sits in the middle of the US filing season. A disposal made on 4 April and one made on 7 April fall in different UK tax years but the same US calendar year, which changes when UK tax is paid and therefore when a foreign tax credit becomes available.
The 31 January UK balancing payment and 31 July payment on account are UK cash outflows that determine the timing of creditable foreign tax, and they sit two weeks and six weeks respectively away from US estimated tax dates.
ISA subscriptions must be made by 5 April to use the allowance, which is 20,000 pounds for the 2026 to 2027 tax year per gov.uk/individual-savings-accounts. An ISA is UK tax free and US taxable, and the funds inside it are usually PFICs, so a purely UK-optimal 5 April action creates US reporting in the following filing cycle.
Pension contributions made before 5 April to manage a UK annual allowance position may generate a pension savings statement that does not have to arrive until 6 October, which is after the June 15 date and only just before October 15.
The FBAR is a calendar-year filing on calendar-year balances, while the UK bank and platform reporting underneath it is produced on a 5 April cycle. The reconciliation is manual, every year, for every account.
UK employment benefits are not final until the 6 July P11D, but US employment income for the calendar year needs January to December figures, so two partial UK tax years always have to be spliced.

A Worked Scenario: One Investor, One Compliance Year

The following is an illustration, not a client file, and the figures are illustrative. Assume a US citizen, UK resident for eleven years, married filing separately. She holds a UK current account and two savings accounts with a combined peak balance of around 180,000 US dollars during the year, a UK investment platform holding six OEICs and two investment trusts worth roughly 900,000 US dollars, a 30 percent shareholding in a UK limited company through which she consults, a stocks and shares ISA, and a workplace pension. In March she received a gift of 140,000 US dollars equivalent from her UK-resident father. Where sterling amounts are converted, assume a single consistently applied posted rate, documented at the start of the year, as the IRS permits.

Her triage produces: an FBAR, because aggregate balances comfortably exceeded 10,000 US dollars; Form 8938, because her specified foreign financial assets exceed both the 200,000 US dollar year-end and the 300,000 US dollar any-time thresholds for a married-filing-separately taxpayer abroad; Form 8621 for each of the eight pooled holdings, including the funds inside the ISA, with the two that made distributions requiring filings regardless of any exception; a Form 5471 analysis on the 30 percent shareholding against the filer categories at irs.gov/forms-pubs/about-form-5471; and Form 3520 Part IV, because the gift from a nonresident alien individual exceeds 100,000 US dollars in aggregate for the year, with each component over 5,000 US dollars separately identified. She has no US withholding, so all four estimated tax dates apply.

Sequenced by data availability rather than by deadline, her year runs: January, pay the Q4 estimate, gather balances, file the FBAR, issue PFIC data requests to the platform and to two fund managers, and document the gift. April 15, pay the prior year balance and the Q1 estimate. Late May, P60 arrives and employment income is rebuilt across two UK tax years. June 15, file Form 4868 with the line 8 box checked and pay the Q2 estimate. Early July, P11D closes the benefits position. July and August, the UK company's accounts support the Form 5471 work and the PFIC computations are built. September 15, Q3 estimate. Early October, the pension savings statement is checked. October 15, the 1040 is filed with Forms 8938, 8621 and 5471 attached and the Form 3520 goes in separately, because that is its final possible date. The only item that could realistically have been finished in January was the FBAR, and it was.

State Filing Where a US State Connection Persists

Federal deadline calendars almost universally exclude state filing, and for a departed US person that exclusion is where problems accumulate. States set their own residency rules, their own deadlines and their own extension mechanics, and some do not recognise the federal automatic extension for taxpayers abroad at all. A continuing state connection can survive a move abroad through a retained home, a driving licence, voter registration, in-state source income such as rental property, or simply never having filed a final part-year return. None of that is resolved by the federal calendar above. It is a separate annual item and it belongs in the January triage alongside the federal questions, because a state deadline that does not shift to June 15 will be missed by anyone running a purely federal diary.

How We Sequence a Compliance Year

The preparation discipline that keeps a cross-border investor out of trouble is not complicated, but it has to be applied in a fixed order and started earlier than most people expect.

Run the triage in January against actual current holdings, not against last year's form set, and record which mid-year events occurred.
File the FBAR in the first quarter, before the UK documents cycle begins, and stop treating October 15 as its date.
Chase PFIC and entity data in January, because these are the only inputs with no statutory production deadline at all.
Fix the currency convention once and apply it identically across the 1040, Form 8938 and the FBAR.
Pay by April 15 on the best available estimate, then extend the filing to October 15 as a default rather than as a rescue.
Attach the required statement when relying on the automatic two-month extension, and check the out-of-country box on Form 4868.
Diary Form 3520 separately, because its extension stops at October 15 even where the income tax return runs to December 15.
Reserve the discretionary December 15 request for genuine data failures, and post the letter before October 15.

Where filings have already been missed, the position is retrievable but it is a separate exercise from the annual calendar and it should not be bolted onto a current-year return without deciding the route first. The IRS states that where it has not contacted you about a late FBAR and you are not under civil or criminal investigation, you should file late FBARs as soon as possible to keep potential penalties to a minimum, and late FBARs are submitted through FinCEN's BSA E-Filing System with a reason for late filing given. Where income was also unreported, the Streamlined Filing Compliance Procedures are the route to consider, and eligibility has to be established before anything is filed. Either way, the fix belongs in its own project plan, and the twelve-month calendar above is what stops it ever being needed again.