If you are a US citizen or resident alien living and working outside the United States and Puerto Rico on the regular due date of your return, you receive an automatic two-month extension to file — generally to 15 June for calendar-year filers. You do not file a form to get it. You simply attach a statement to your return explaining that you qualify as a person described in Treasury Regulation 1.6081-5(a). From there, Form 4868 extends you to 15 October, and a discretionary letter request can reach 15 December. Form 2350 does something different again: it extends your deadline until you can actually qualify for the foreign earned income exclusion.
The critical point, and the one that costs Americans abroad real money every year, is that none of these are extensions to pay. Your tax is still due on the April deadline. Interest accrues from that date on anything unpaid, no matter which extension you are sitting on. This guide sets out what each extension buys you, what it does not, and which one fits your situation.
The automatic two-month extension: what it is and who gets it
The automatic extension to 15 June is the foundation of the expat filing calendar, and it is genuinely automatic — there is no application, no form, and no approval. It applies if, on the regular due date of your return, you are a US citizen or resident alien and either you live outside the United States and Puerto Rico and your main place of business or post of duty is outside the United States and Puerto Rico, or you are in military or naval service on duty outside the United States and Puerto Rico.
The mechanics are simple but easy to get wrong. You claim the extension by attaching a statement to the return you eventually file, confirming which of those two situations applied to you on the due date. The return needs to be filed by 15 June for the extension to have done its job. The IRS guidance for citizens and resident aliens abroad confirms you do not need to file Form 4868 to obtain this two-month period — Form 4868 is only needed if you want time beyond it.
The trap: an extension to file is not an extension to pay
This is the single most important sentence in this guide. Every extension discussed here moves your *filing* deadline. None of them moves your *payment* deadline. Your tax liability for the year is due in April, and interest starts running on any unpaid balance from that date forward, regardless of how much extra filing time you have secured.
The two-month automatic extension has a particular wrinkle here that catches people out. Because it is an extension of time to file only, interest is charged on any tax not paid by the regular April due date — right through the two-month period, even though you are not late in any meaningful sense and have done nothing wrong. If you expect to owe, the way to stop the interest clock is to pay an estimate in April, not to wait until you file in June.
Form 4868: buying time to 15 October
If the two months to June are not enough, Form 4868 is the standard answer. It is the Application for Automatic Extension of Time to File a US Individual Income Tax Return, and it extends a calendar-year filer to 15 October. Like the two-month extension, it is automatic in the sense that the IRS does not evaluate your reasons — you are not asking permission, you are giving notice.
Two details matter for Americans abroad. First, the IRS's Form 4868 guidance covers Forms 1040, 1040-NR and 1040-NR-EZ, so it works whether you are filing as a citizen abroad or as a non-resident alien. Second, the six months run from the *regular* April due date, not from your extended June date — so Form 4868 takes you to October, not to December. Filing it does not stack on top of the automatic two months to give you eight.
Form 2350: the one that is genuinely different
Form 2350 is not a general-purpose extension and should not be treated as a longer Form 4868. It exists for one specific problem: you expect to claim the foreign earned income exclusion, but you have not yet been abroad long enough to meet either the bona fide residence test or the physical presence test.
That situation is common for anyone who moved abroad partway through a year. If you relocated to London in, say, August, you cannot meet the 330-day physical presence test for that tax year until well into the following one — and you cannot claim the exclusion until you meet a test. Form 2350 lets you extend your filing deadline until roughly 30 days after the date you expect to qualify, so that you can file once, correctly, with the exclusion claimed. The IRS's Form 2350 guidance confirms it is only for taxpayers who expect to file Form 2555 and need the time to meet one of those tests. It must be filed on or before the due date, generally 15 June for those relying on the automatic two-month extension.
Form 4868 or Form 2350? Choosing correctly
The distinction is about *why* you need more time, not how much you need. Form 4868 is for the ordinary case: your information is not ready, your UK figures are not final, your broker has not issued corrected statements. Form 2350 is for the structural case: no amount of paperwork readiness helps, because the calendar itself has not yet delivered your qualification for the exclusion.
Getting this wrong has real consequences in both directions. Use Form 4868 when you actually needed 2350, and your October deadline may arrive before you qualify for the exclusion — leaving you to file without it and amend later, or to file late. Use Form 2350 when 4868 would have done, and you have made a representation about expecting to qualify for the foreign earned income exclusion that needs to be true. If your entire reason for delay is that you are waiting to hit 330 days abroad, 2350 is the right instrument.
- Form 4868 — general six-month extension from the April due date, to 15 October. Use when your data is not ready.
- Form 2350 — extension until shortly after you expect to meet the bona fide residence or physical presence test. Use only when you expect to file Form 2555.
- Neither extends the time to pay. Both require a good-faith estimate of liability and payment to stop interest.
The December 15 discretionary extension
Beyond October, there is one further option that is not widely known: a discretionary two-month extension to 15 December, available to taxpayers who are out of the country. Unlike everything above, this one is genuinely discretionary — the IRS can say no.
You request it by writing to the IRS before the October deadline expires, explaining the reasons you need the additional time. There is no form. Because it is discretionary, you do not receive confirmation that it has been granted in the way you would with an automatic extension; the IRS generally only contacts you if the request is denied. That asymmetry makes it a slightly uncomfortable instrument to rely on, and it is best treated as a genuine last resort rather than as a routine part of the filing calendar.
How the FBAR deadline fits alongside all this
The FBAR — FinCEN Form 114 — runs on its own track and does not follow your income tax extensions at all. Its due date is aligned with the April tax deadline, but it carries its own automatic extension to 15 October, granted to everyone, with no request needed and no statement to attach.
The practical effect is that an American abroad who extends to October has their 1040 and their FBAR landing on the same day, which is convenient. But an American who files their return in June under the automatic two-month extension still has until October for the FBAR — and one who obtains a December extension for their return does *not* get the FBAR pushed to December with it. If you are unclear on whether you need to file at all, our FBAR and FinCEN 114 guide covers the thresholds and the account types that count.
State deadlines do not move with the federal ones
If you still have a state filing obligation, do not assume the federal extension carries across. States set their own rules: some grant an automatic extension when you have a federal one, some require their own form, and some have entirely different dates. The automatic two-month extension for taxpayers abroad is a federal creation and has no necessary state equivalent at all.
This catches Americans who have moved abroad but have not cleanly severed state residence — a live issue for anyone who left California, New York or Virginia without establishing domicile elsewhere. Our guide to state tax for Americans abroad covers which states pursue former residents and how to establish that you have genuinely left.
Penalties: what late filing actually costs
There are two separate penalties and they behave differently, which is precisely why extensions are worth taking even when you cannot pay. The failure-to-file penalty is the aggressive one — it accrues at a far higher monthly rate than the failure-to-pay penalty. A valid extension eliminates the failure-to-file penalty entirely for the extended period.
The failure-to-pay penalty, plus interest, continues to accrue on unpaid tax from April regardless. So the arithmetic for an American abroad who owes money and is not ready to file is straightforward: extend, and pay whatever estimate you can. Extending costs nothing and removes the larger penalty. Paying an estimate reduces the smaller one. Doing neither exposes you to both, which is the worst of every available outcome.
Estimating what to pay in April when your figures are not final
The obvious objection to 'pay an estimate in April' is that if you knew your number you would have filed. But an extension request is expected to carry a good-faith estimate of liability, and a reasonable approximation is usually achievable long before a return is finalised — particularly for expats whose income is largely salary and whose exclusion position is broadly known.
Where the number is genuinely uncertain, erring high is usually the cheaper mistake. Overpaying means the excess is refunded or applied forward with no penalty; underpaying means interest and failure-to-pay penalties on the shortfall. If you are also making quarterly payments, our US quarterly estimated tax calculator can help you size the April payment, and our foreign earned income exclusion calculator will give you a realistic view of how much of your foreign salary is actually going to be excluded before you guess at the balance.
What extensions do not fix
An extension buys time on one specific obligation: filing your income tax return. It does not extend the time to make certain elections, it does not extend contribution deadlines that are tied to the original due date, and it does not help with returns you should have filed in earlier years.
That last point deserves emphasis. If you are behind by several years, extensions are not the remedy — they only ever apply to the current year's return. Americans who discover they have not been filing while abroad need the IRS Streamlined Filing Compliance Procedures, which is a distinct programme designed for exactly that situation and carries no penalty for non-wilful failures. Filing an extension for this year while ignoring six missing prior years addresses the smaller problem and leaves the larger one running.
- Extensions apply to the current year's return only — they do nothing for prior unfiled years.
- The payment deadline never moves, whichever extension you use.
- FBAR has its own automatic October extension and does not follow your 1040 extension.
- State deadlines follow state rules, not the federal expat extension.
- A discretionary December extension can be refused; automatic extensions cannot.
Building your filing calendar
For most Americans in the UK, the practical shape of the year is this. In April, estimate and pay. In June, file if you can — the automatic extension has already given you the time without any paperwork. If you cannot, file Form 4868 to reach October, unless your specific problem is that you have not yet qualified for the foreign earned income exclusion, in which case Form 2350 is the correct form and 15 June is its deadline.
Working around a UK tax year that ends on 5 April makes this harder than it is for a US-domestic filer, because your UK figures for the overlapping year often are not final until well after the US April deadline — which is exactly the situation the two-month extension was designed for. Our guide to US tax return deadlines for 2026 sets out the full calendar with the UK dates alongside.
