Every US citizen and Green Card holder files a Form 1040 on worldwide income regardless of where they live, if income exceeds the filing threshold. Filers abroad get an automatic extension to 15 June, extendable to 15 October. Tax owed is still due in April. Most owe nothing after the foreign earned income exclusion ($132,900 for 2026) or the foreign tax credit — but must still file.
The United States is one of very few countries taxing on citizenship rather than residence. The practical consequence is that leaving does not end the obligation, and that people who have never lived in America — accidental Americans born there or to American parents — carry it too.
Filing is required even when no tax is due. That surprises people, and it is the root of most catch-up cases: the liability was always nil, so nobody filed, and the unfiled information returns quietly accumulated penalties that have nothing to do with tax owed.
| Date | What it is |
|---|---|
| 15 April | Payment deadline. Interest runs from here even though filing is extended |
| 15 June | Automatic filing extension for taxpayers whose tax home is abroad — no form needed |
| 15 October | Extended deadline if Form 4868 is filed |
| 15 December | Discretionary further extension, requested by letter |
| 15 April (FBAR) | FBAR due date, with an automatic extension to 15 October |
The June extension is automatic but it is not an extension to pay. Interest accrues from April on anything owed, which matters in years with a large one-off gain.
The foreign earned income exclusion removes up to $132,900 of earned income from US tax for 2026, via Form 2555. The foreign tax credit instead offsets US tax with foreign tax actually paid, via Form 1116. You can use both, but not on the same income.
For an American in a high-tax country such as the UK, the credit is usually better, because UK tax exceeds US tax and the excess builds a carryover with a ten-year life. The exclusion wastes that — you exclude the income, so the UK tax on it generates no creditable credit.
The exclusion also has a trap: revoking it bars you from re-electing for five years without IRS consent. It is a decade-long decision made on a single year's numbers, and it is frequently made by software default.
The 1040 is rarely where the cost is. The information returns are, because their penalties are fixed dollar amounts that apply whether or not tax is due.
| Form | Triggered by | Typical penalty for failure |
|---|---|---|
| FinCEN 114 (FBAR) | Foreign accounts over $10,000 aggregate | Up to $10,000 per report, non-willful |
| 8938 | Specified foreign assets over threshold | $10,000, rising to $50,000 |
| 5471 | Interest in a foreign corporation, incl. a UK Ltd | $10,000 per form per year |
| 8621 | PFICs — most non-US funds, including inside an ISA | Keeps the statute open |
| 3520 / 3520-A | Foreign trusts and large foreign gifts | Up to 25% of the amount |
Leaving the country does not automatically end a state filing obligation. States apply their own residency and domicile rules, and a few — California, New Mexico, South Carolina and Virginia are the usual examples — are difficult to leave while retaining ties such as a property, a driving licence or voter registration.
No treaty reaches state tax. The US–UK treaty binds the federal government only, so state tax on income the treaty allocates to Britain is simply payable.
We build the UK position first where there is one, because the credit depends on it. Then the election decision is modelled across both systems over a multi-year horizon rather than for the filing year alone, and the information returns are identified from the underlying facts rather than from what the client thought to mention.
Every return is signed by a licensed professional with unlimited practice rights before the IRS, so if a question arrives later the person who prepared it can answer it.
Yes, if your income exceeds the ordinary filing threshold. The obligation is to file, not merely to pay, and most expat penalties attach to unfiled information returns rather than unpaid tax. A nil liability is the usual outcome, not a reason to skip the return.
$132,900 per qualifying person, claimed on Form 2555. It covers earned income only — salary and self-employment profit — and does nothing for dividends, interest, rent or capital gains. You must meet either the bona fide residence test or the physical presence test of 330 full days abroad in a 12-month period.
In a high-tax country such as the UK, usually the credit. It offsets US tax with UK tax paid and banks the excess as a carryover for up to ten years, whereas the exclusion removes the income and wastes the associated foreign tax. In a no-tax country such as the UAE the exclusion is normally better, because there is no foreign tax to credit.
You get an automatic extension to 15 June with no form required, and can extend to 15 October with Form 4868. Payment is still due on 15 April, so interest accrues from that date on anything owed. A further discretionary extension to 15 December can be requested by letter.
The streamlined foreign offshore procedures usually resolve it: three years of returns, six years of FBARs, no penalty where the failure was non-willful. Establish eligibility before preparing anything, because the route determines how many years you file and what the certification has to say.
Possibly. States set their own residency rules and no tax treaty reaches them, so a state can tax income the federal treaty allocates elsewhere. California, New Mexico, South Carolina and Virginia are the ones that most often continue to assert residency after departure, particularly where property, a licence or voter registration remain.
The exclusion-versus-credit decision is worth more than the return itself. We model both before filing either.
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