Married to a Brit (or an American)? How a US/UK Couple Should Plan Their Taxes

When one spouse is a US citizen and the other isn't, the couple doesn't get one tax position — it gets several, and the American spouse's choices affect the other person's finances. The US taxes its citizens on worldwide income wherever they live, and it applies that rule to the individual, not the household. Marrying a Brit doesn't make your spouse a US taxpayer, but it does create decisions you wouldn't face if you were single or both American.

The first decision: how does the American spouse file?

A US citizen married to a non-US spouse who lives abroad has two realistic filing options:

• Married filing separately. You report only your own income. Your spouse stays outside the US tax system, and their income and accounts aren't reported on your return. The trade-off is that separate filing generally comes with less favorable thresholds and rates than joint filing.
• Married filing jointly by election. You can elect to treat your non-US spouse as a US tax resident for the whole year. Their worldwide income then goes on the joint return, which can unlock joint-filing rates, but it also brings their accounts and income under US reporting, and the election carries into later years until it is revoked.

Neither is automatically right. Where one spouse earns most of the income, joint filing can reduce the tax bill. Where the non-US spouse has significant savings, investments or a business, the reporting and tax exposure the election creates often outweighs the benefit. This is a numbers question, and it's worth running both ways before the first return rather than defaulting to whichever the software suggests. Our US tax return service models both options for exactly this reason.

Joint accounts: whose money is it, for reporting purposes?

Reporting rules follow ownership and access, not who earned the money. For the FBAR, a joint account you co-own or can sign on is generally reported by you at its full value, not half, even though your spouse has no US filing obligation at all. The same account may also count toward your Form 8938 thresholds. The practical consequence is that a couple with a shared UK current account and a shared savings account can cross the FBAR threshold on the joint accounts alone. We cover the mechanics in our guide to FBAR vs Form 8938.

Gifts and transfers between spouses

Between two US-citizen spouses, transfers are generally unlimited and untaxed. When the recipient spouse isn't a US citizen, that unlimited marital deduction doesn't apply. Instead, gifts to a non-citizen spouse are limited by an annual exclusion amount that the IRS adjusts each year, and larger gifts may need a gift tax return (Form 709) even where no tax is actually payable. Check the current annual figure on IRS.gov before moving a large sum, such as funding a joint property purchase or topping up a spouse's savings. Our gift tax service handles the filing side of this.

Property, savings and investments in the UK spouse's name

Assets held only by the non-US spouse mostly stay outside your US return, but there are two exceptions worth knowing. If you contribute to them, or have access to them, the reporting picture can change. And investments you hold jointly, particularly UK funds and ISAs, can bring in the PFIC rules covered in our post on why your ISA is a problem on your US tax return. Buying a home together is another moment to check the position, as UK property held jointly raises questions on both the US and UK sides. Our cross-border property service covers those.

Estate planning for a mixed couple

The same asymmetry that applies to gifts applies to estates. The US marital deduction for transfers at death is available for a US-citizen spouse but restricted for a non-citizen spouse unless a specific type of trust is used. The UK's spouse exemption depends on each spouse's domicile for inheritance tax purposes, and those rules have been changing. Wills drafted in one country often don't work as intended in the other, so a couple with assets in both should have their estate plans reviewed together. Our guidance for families and mixed couples and our trusts and estates service cover the planning side.

Illustrative example: an American in the UK married to a British spouse holds a joint current account and a UK stocks and shares ISA in the American's name. They file separately to keep the British spouse outside the US system. The joint account is reported by the American in full on the FBAR, and the ISA is treated under the PFIC rules. Had they elected joint filing, the British spouse's own savings would have come under US reporting as well. This is illustrative only; the right answer depends on the couple's actual income and assets.

The bottom line

The American spouse's tax obligations are personal to them, but the household's choices shape those obligations: the filing status, how accounts are titled, how gifts and inheritances are structured. Making those choices deliberately, once, is much cheaper than untangling a default that didn't fit.