A US citizen married to a British spouse who is not a US citizen or resident usually files as married filing separately. Two other statuses may be available: head of household, where there is a qualifying child or other qualifying person, and married filing jointly, where the couple elect to treat the non-US spouse as a US resident. Single is not an option for someone who is married at the end of the year.
This article is for Americans in the UK whose husband or wife has no US status. It extends the section on spouses in our guide to US and UK tax returns for Americans in the UK and covers the three statuses, the cost of the joint election, and the knock-on effects for the standard deduction, Form 8938, gifts between spouses and the FBAR. No status is best for every couple.
Why married filing separately is the default
Married filing separately is the status that applies when a married US citizen does nothing else. The non-US spouse stays outside the US tax system, and the citizen reports only their own income. The gross income filing threshold for this status is $5, so nearly everyone who uses it must file.
That threshold surprises people who have read that a return is needed only above the standard deduction. The figure appears in the IRS filing tables and in Publication 54 (opens the official IRS page in a new tab), and it looks at gross income before any exclusion or credit. A US citizen in the UK with a modest part-time salary, fully taxed under PAYE and wholly covered by the foreign tax credit, still has a Form 1040 to file each year.
The status has real drawbacks. The rate bands are the narrowest, several credits and deductions are restricted or unavailable, and some thresholds elsewhere in the tax code are set lower for separate filers. Against that, it keeps the spouse's salary, savings, pension and investments off the US return. For many couples in the UK, where the citizen's own tax is already covered by credits for UK tax, that separation is worth more than the reliefs given up.
When head of household is available with a non-US spouse
A US citizen married to a non-resident alien can be treated as unmarried for head of household purposes, provided the couple have not elected to treat the spouse as a US resident. The spouse does not count as the qualifying person. There must be someone else, most often a child.
The conditions are specific. The citizen must pay more than half the cost of keeping up the home for the year, counting rent or mortgage interest, council tax, utilities, repairs, insurance and food eaten at home. A qualifying child must generally live in that home for more than half the year. The child must also meet the tests to be the citizen's qualifying person, and a child who is not a US citizen or resident may not meet them.
The half-the-cost test deserves care in a two-income household. If the British spouse earns more and pays most of the household bills, the test may fail however the couple think of their finances. Records of who paid what are the evidence. Where the conditions are met, head of household gives wider rate bands and a larger standard deduction than married filing separately, while still keeping the spouse outside the US system. Where they are not, claiming it is an error that can be reopened.
How the election to file jointly with a non-US spouse works
A couple can choose to treat the non-US spouse as a US resident for income tax and file a joint return. The choice is made by a statement signed by both spouses and attached to the joint return for the first year it applies. It continues for later years until it ends.
Publication 519 (opens the official IRS page in a new tab) sets out the rules. The statement declares that one spouse was a US citizen or resident and the other a non-resident alien on the last day of the year, and that both choose resident treatment for the whole year. A joint return is required for the first year. In later years the couple may file jointly or separately, but both remain taxable as US residents while the election stands.
The spouse needs a US taxpayer number. Someone who cannot obtain a Social Security number applies for an individual taxpayer identification number (opens the official IRS page in a new tab) on Form W-7 (opens the official IRS page in a new tab), normally sent with the first joint return and supported by a passport or a certified copy. Our form guide to Form W-7 explains the documents. The application adds time to the first year's filing, which matters if a refund is expected.
What the joint election costs
The price of a joint return is that the non-US spouse's worldwide income becomes taxable in the US for every year the election is in force. Their UK salary, savings interest, rental income, ISA income and investment gains all go on the return, with credit for UK tax where the rules allow.
Income is only part of it. The spouse's holdings are measured by US rules, so UK funds in their ISA are commonly passive foreign investment companies with their own form, and their interests in UK companies or trusts can bring information returns. While the election is in effect, neither spouse can generally claim treaty benefits as a resident of the UK, apart from the benefits the treaty preserves for US residents and citizens.
Take a US citizen employed in Bristol whose British wife teaches, contributes to a workplace pension and holds funds in a stocks and shares ISA. Filing separately, none of the wife's income or accounts appears on a US return. Under the election, her salary is reported and largely covered by credit for UK tax, but the ISA funds need annual US reporting and may produce US tax that the UK does not charge. Whether the larger deduction outweighs that depends on the figures, which is why our individual tax returns work models both before the first joint return is filed.
- Either spouse can revoke the election in writing, which ends it for both
- It ends on the death of either spouse or on legal separation
- The IRS can end it if adequate records are not kept
- It is suspended for any year in which neither spouse is a US citizen or resident
- Once ended, neither spouse can make the election again, even with a different spouse
How filing status changes the standard deduction and Form 8938
Filing status sets the standard deduction and the Form 8938 threshold. For tax year 2025 the standard deduction is $15,750 for a married person filing separately, the same as for a single filer, and $31,500 on a joint return. Head of household falls between the two.
The deduction matters less in the UK than the comparison suggests. A US citizen whose UK tax exceeds the US tax on the same income already has a nil US liability on that income through the foreign tax credit, and a larger deduction then saves nothing more. It matters where there is income the UK does not tax, or taxes lightly, since that is where US tax is actually paid. The joint figure is also shared with the spouse's income once that income is on the return.
The thresholds for Form 8938 move with status as well. The IRS comparison of Form 8938 and FBAR requirements (opens the official IRS page in a new tab) gives the figures for a taxpayer living abroad: $200,000 at year end or $300,000 at any time for a person not filing jointly, and $400,000 at year end or $600,000 at any time on a joint return. The joint threshold is higher, but under the election the spouse's foreign financial assets count towards it and are listed on the form, so the form often becomes longer and not shorter.
Gifts to a non-citizen spouse and joint accounts on the FBAR
Transfers between spouses are not free of US gift tax when the recipient is not a US citizen. The unlimited marital deduction is unavailable, and the annual exclusion for gifts to a non-citizen spouse is $190,000 for 2025. The joint filing election does not change this, because the rule turns on citizenship.
The IRS guidance on gift tax (opens the official IRS page in a new tab) explains the exclusion. A gift above it is reported on Form 709 (opens the official IRS page in a new tab) and uses part of the giver's lifetime exemption, so tax is rarely payable but a return is due. Paying money into a joint bank account is generally not a completed gift until the other spouse draws on it for their own benefit. Buying a home or investments in joint names follows different rules and should be checked before completion. Our gift tax returns service and the form guide to Form 709 cover the detail.
Joint accounts also affect the FBAR. A US citizen reports the full value of an account held jointly with a non-US spouse, not half, and it counts in full towards the aggregate threshold. FinCEN's page on reporting foreign bank and financial accounts (opens the official FinCEN page in a new tab) sets out who files. The joint filing election is an income tax election and does not generally make the spouse a US person for FBAR purposes. Our article on whether you file the FBAR or Form 8938 compares the two reports, our foreign income and FBAR service prepares them, and the guide for Americans in the UK sets the family rules in context.
- The spouse's own income, UK funds, pension and any company or trust interests
- Whether there is a qualifying person and who pays the household costs
- How much US tax the citizen actually pays after credits for UK tax
- Planned transfers between spouses, including property purchases
- Whether the couple expect to stay in the UK or move to the US
General information, not advice. The right answer depends on your circumstances and the tax year concerned.
