Married to a Non-American: How US Citizens Abroad File With a Foreign Spouse

A US citizen married to a non-American usually files Married Filing Separately: the spouse stays entirely outside the US tax system, and only the American's own income, accounts and assets are reported to the IRS. The main alternative — a section 6013(g) election to treat the non-resident spouse as a US resident and file jointly — buys better rates and a full joint standard deduction at the cost of pulling the spouse's worldwide income and financial life into the US net. For a high-earning British spouse that trade is usually a poor one, but it is a decision that deserves an actual analysis, not a default.

Key takeaways

• Marrying a US citizen does not, by itself, make anyone a US taxpayer. A non-resident alien (NRA) spouse stays outside the system unless the couple elects otherwise.
• Married Filing Separately is the standard answer for Americans abroad with a non-US spouse — but its filing threshold is far lower than for other statuses, so a return is due on almost any income.
• The section 6013(g) election is powerful and sticky: joint rates in, the spouse's worldwide income and reporting in — and once revoked, it can never be made again with the same spouse.
• Head of Household is sometimes available to an American who is considered unmarried and maintains a home for a qualifying child — better brackets than MFS without touching the spouse.
• Joint UK accounts pull the American in for FBAR purposes, even though the spouse's own sole-name accounts stay out.
• Transfers to a non-citizen spouse do not enjoy the unlimited marital deduction — above an annual limit, gifts become reportable.

The default position: your spouse stays outside the US system

US tax follows the person, not the marriage. A British, French or Emirati spouse with no US citizenship, no green card and no US residency is a non-resident alien in IRS language, and their salary, business, investments and bank accounts are simply none of the IRS's business — provided the couple does nothing to change that.

What the marriage does change is the American's filing status. "Single" is no longer available, and a normal joint return requires both spouses to be US persons. That leaves Married Filing Separately as the default for most US citizens abroad with a non-American spouse.

MFS has real drawbacks. The brackets are the least favourable of any status, several credits and benefits are reduced or unavailable, and — the trap that catches people first — the filing threshold for MFS is dramatically lower than for single or joint filers. In practice, almost any gross income at all means a return is due, even for an American whose earnings would be fully sheltered by the foreign earned income exclusion or foreign tax credits. Filing is still required to claim those reliefs; they do not apply themselves.

For most couples where the non-US spouse has meaningful UK income, MFS is the right answer precisely because of what it doesn't do: it keeps the spouse's earnings, ISAs, pensions and accounts entirely off the US return.

The section 6013(g) election: joint filing at a price

Section 6013(g) of the Internal Revenue Code lets a US citizen or resident who is married to a non-resident alien elect to treat that spouse as a US resident for income tax purposes. The couple then files jointly, with joint rates and the full joint standard deduction. The IRS sets out the mechanics on its nonresident spouse treated as a resident page.

The price is the other half of the sentence: the spouse is treated as a US resident, so their worldwide income goes on the return and their financial life enters the US reporting perimeter. For a British spouse that typically means UK salary, self-employment income or dividends becoming US-taxable (with foreign tax credits doing the heavy lifting), UK investment funds raising PFIC questions, and pensions requiring analysis rather than assumption.

The decision usually turns on a handful of drivers:

• The spouse's income level. A non-working or low-earning spouse brings little income into the net while unlocking joint rates and deductions — here the election can genuinely help. A high-earning UK spouse brings a full UK financial life into a second tax system for a modest rate benefit — usually a bad trade.
• What the spouse owns. UK funds, ETFs and stocks-and-shares ISAs held by the spouse can become PFIC problems overnight under the election. Cash savings and UK-taxed employment income are far more benign.
• Permanence. The election continues from year to year until it is suspended, revoked or terminated — and once revoked, it can never be made again with the same spouse. It is a one-way door, not an annual choice.
• The compliance load. Two worldwide-income taxpayers means more forms, more reconciliation between UK and US tax years, and more that can go wrong.

There is no universal answer, which is why the election should be modelled both ways before anyone signs anything. This is core US-UK expat tax territory.

ITIN or SSN: getting your spouse a number — when you actually need one

A joint return — including the first year of a 6013(g) election — requires the non-US spouse to have a taxpayer identification number: a Social Security number if they are eligible for one, otherwise an Individual Taxpayer Identification Number (ITIN), applied for on Form W-7 and usually submitted together with the return it supports, along with certified identity documents.

Filing separately generally does not force the spouse into the numbering system: an American filing MFS whose NRA spouse has no US filing requirement of their own can typically indicate the spouse's non-resident status instead, though the mechanics differ between paper and electronic filing. An ITIN is an identification number only — holding one does not by itself create US tax obligations. The practical point: don't apply for a number until the filing-status question is decided, because the number follows the strategy, not the other way round.

Head of Household: the overlooked third option

An American married to a non-resident alien can, for tax purposes, be considered unmarried — and if they also maintain a home for a qualifying child or other qualifying person and meet the status tests, Head of Household may be available. HoH offers better brackets and a larger standard deduction than MFS, while still leaving the spouse completely outside the US system.

For a US citizen in London with children and a British spouse, this is often the best of both worlds. The tests are specific — who counts as a qualifying person, who paid the costs of keeping up the home — so treat it as an option to be checked against the facts, not assumed.

Joint UK accounts: where your spouse's money meets your FBAR

The FBAR runs on ownership and signature authority, not on filing status. Your spouse's sole-name accounts stay off your FBAR. But the moment an account is joint — the household current account, a joint savings pot, an offset account behind the mortgage — the American holds a financial interest and reports the account, generally at its full maximum value, once the aggregate reporting threshold is met. The same applies to accounts in the spouse's sole name over which the American merely holds signature authority.

Couples get this wrong constantly, usually on the theory that "it's mostly my spouse's money". The FBAR does not care. If joint accounts have gone unreported for years, start with our missed FBAR guide — the fix is usually manageable if it is done properly and promptly.

Whether the 6013(g) election changes the spouse's own FBAR position is a narrower technical question than most articles admit — the FBAR has its own definition of who must file, separate from the income tax election — and it belongs in a professional conversation, not a blog paragraph.

Gifts between spouses: the citizenship catch

Married Americans are used to moving money between spouses freely, because transfers to a citizen spouse enjoy an unlimited marital deduction. Transfers to a non-citizen spouse do not. Instead there is an enhanced annual exclusion for gifts to a non-citizen spouse — larger than the ordinary annual gift exclusion, but a limit all the same, and it adjusts over time. The IRS's gift tax pages set out the framework.

This matters in mundane situations: moving savings into the British spouse's name (perhaps precisely to avoid PFIC or FBAR complications), adding a spouse to the deeds of a house, funding a spouse's business. Each can become a reportable gift once the annual limit is passed. Usually the result is a filing rather than a tax bill — but unfiled gift returns age badly.

The same citizenship distinction cuts far deeper at death, where the estate-tax marital deduction is also restricted for a non-citizen surviving spouse. That is a planning topic in its own right — see our guide to US estate and gift tax for Americans in the UK.

Got it wrong for years? There is a clean way back

The recurring patterns are familiar: filed as single for a decade; claimed credits that MFS does not allow; stopped filing altogether on the theory that "my spouse earns the money"; or filed correctly but never reported the joint accounts. None of these improves with time — and under FATCA, UK banks are already reporting US-linked accounts to the IRS.

For non-willful cases, the Streamlined Filing Compliance Procedures exist for exactly this: a defined look-back of returns and FBARs, a certification of non-willfulness, and penalty protection that quiet catch-up filing does not offer. Our plain-English guide to streamlined filing for US expats walks through eligibility and the package.

Deciding properly

The filing-status question for a mixed-nationality couple is a genuine planning decision — MFS, the 6013(g) election, or Head of Household — layered with FBAR, gift and estate consequences that never appear on a tax return until, suddenly, they do. At Next Tax Source this is private-client work: a licensed CPA or Enrolled Agent reviews and signs off every return and every election recommendation before it goes anywhere. If you are newly married, newly abroad, or quietly aware that past years were filed wrong, book a confidential consultation and we will map the options against your actual numbers.

This article is general information, not tax advice, and does not create a professional relationship. Thresholds, exclusions and election mechanics change; confirm the current position with a licensed professional before acting.

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Reviewed by a CPA / Enrolled Agent. Last updated: 4 September 2026.

Official sources: IRS — Nonresident Spouse Treated as a Resident | IRS — Individual Taxpayer Identification Number (ITIN) | IRS — Report of Foreign Bank and Financial Accounts (FBAR) | IRS — Gift Tax