A British husband or wife needs an individual taxpayer identification number when they must appear on a US return with a taxpayer number and cannot get a Social Security number. For most couples in the UK that comes down to one situation: electing to treat the non-US spouse as a US resident and filing a joint return. A married filing separately return does not need one, and a head of household claim does not rely on the spouse at all.
This post is for US citizens and green card holders in the UK married to someone with no US status. It sits under our guide to US and UK tax returns for Americans in the UK and assumes the filing status is settled, which our post on which US filing status applies when you are married to a Brit covers. Here we deal with the number itself: when it is required, when it is not, children, applying on Form W-7 (opens the official IRS page in a new tab) from Britain, and what happens to an ITIN that falls out of use.
When a British spouse needs an ITIN
A non-US spouse needs an ITIN when the couple file jointly under the election to treat them as a US resident, or when the spouse must file a US return of their own. In both cases the spouse is not eligible for a Social Security number, so an ITIN is the only taxpayer number open to them.
The joint election is the common case. Publication 519 (opens the official IRS page in a new tab) says the statement making the choice must give the name, address and taxpayer number of each spouse, signed by both and attached to the joint return for the first year the choice applies. The Form 1040 (opens the official IRS page in a new tab) filing status section now has a box to check for this choice, with the spouse's name entered beside it. A joint return without the spouse's number cannot be processed as one, which is why the application travels with it.
The second case is a spouse with US income of their own. A British spouse who owns a let flat in Florida, for example, may have to file Form 1040-NR as a non-resident and needs a number for it. The IRS ITIN pages (opens the official IRS page in a new tab) set the general test: the person has a federal tax purpose, such as a filing requirement or being claimed as a spouse for a tax benefit, and is not eligible for a Social Security number. A spouse who already holds a Social Security number from earlier time in the US uses that number instead.
- A joint return under the election to treat the spouse as a US resident
- The spouse's own Form 1040-NR for US rental, business or other income that requires a return
- A refund claim or treaty benefit for which the spouse must give a US number
When you can file without an ITIN for your spouse
On a married filing separately return, a spouse who has no taxpayer number and is not required to have one is shown as a non-resident alien. The IRS instructions for Form 1040 say to enter NRA in the space for the spouse's number. No Form W-7 is needed, and the return is filed in the usual way.
The Form W-7 instructions point the same way from the other side. Since the personal exemption for a spouse ended after 2017, a spouse generally needs an ITIN only when claimed for an allowable tax benefit, such as a joint return, or when filing their own return. A British spouse with no US income and no benefit claimed has no basis for an application.
Head of household works the same way. Publication 501 (opens the official IRS page in a new tab) treats a US citizen as unmarried for this status if the spouse was a non-resident alien and no election to treat the spouse as resident was made, but it also says the spouse is not a qualifying person. The qualifying person is usually a child, so it is the child's number that matters, as the next section explains. The number is not needed to buy time either: the IRS ITIN pages allow an extension request or an estimated payment to be made before it exists, marked ITIN TO BE REQUESTED.
Whether your children need an ITIN
Usually not. A child who acquired US citizenship through an American parent is eligible for a Social Security number and should have one instead. A child who is not a US citizen or resident and lives in the UK generally cannot be claimed as a dependant at all, so there is no tax purpose for an ITIN.
The Form 1040 instructions ask whether a child was a US citizen, US national, US resident alien or a resident of Canada or Mexico. A British child living in London who is none of these fails that test. The exception is an adopted child: a US citizen whose adopted child lived with them all year meets the citizenship requirement for that child, and the W-7 instructions say such a child may be eligible for an ITIN where a request for an adoption taxpayer number was refused.
The type of number also decides the credits. The child tax credit (opens the official IRS page in a new tab) requires a valid Social Security number for the child, so an ITIN does not secure it, and the W-7 instructions say a dependant claimed for the credit for other dependents must be a US resident or US national. Our post on the child tax credit for American families in Britain covers the Social Security number rules in detail.
- US citizen child: apply for a Social Security number, not an ITIN
- Non-citizen child living in the UK: generally not a dependant on a US return
- Adopted child who lived with a US citizen parent all year: may qualify, with an ITIN if an adoption number was refused
- Spouse: never a dependant, whatever the filing status
How to apply for an ITIN from the UK
From Britain there are two practical routes: post Form W-7, the return and the identity documents to the IRS ITIN unit in Austin, Texas, or use a Certifying Acceptance Agent, who checks the documents and hands them straight back. The IRS walk-in centres that verify documents operate only in the United States.
The documents are the hard part. The W-7 instructions require originals or copies certified by the agency that issued them, carrying its official seal. A copy certified by a solicitor, a notary or a bank does not meet that rule. A current passport is the one document that proves identity and foreign status on its own. Without one, a combination of other current documents is needed, generally including one with a photograph.
Posting an original passport means going without it while the IRS holds it. The IRS says documents are returned to the mailing address on the W-7, and the instructions allow a prepaid courier envelope to speed that up. A Certifying Acceptance Agent avoids the problem: the IRS lists these agents as available in the US and internationally, they can verify originals and certified copies for a spouse, and the passport goes back at the appointment.
The W-7 instructions also say officers at US embassies and consulates abroad provide certification and authentication services, and they ask applicants to contact the consular section in advance. The IRS ITIN pages do not describe what the US Embassy in London currently offers ITIN applicants, so confirm with the embassy before planning around that route. Our form guide to Form W-7 summarises the application.
- Form W-7 signed by the spouse, with the reason box for a spouse checked
- The tax return that needs the number, with the W-7 attached to the front
- An original passport, or a copy certified by the authority that issued it
- For the joint election, the statement signed by both spouses
Attaching Form W-7 to the first joint return
The W-7 goes on the front of the return that needs the number, and the whole package is posted to the ITIN unit. The spouse's number space is left blank. The application must go in by the return's due date, including extensions, and the return is processed once the number is issued.
The IRS asks applicants to allow several weeks to hear about an application, and longer during the peak filing season or when applying from overseas, which covers most applications from the UK. For a couple expecting a refund, that delays it. For a couple who owe tax, interest runs from 15 April whatever happens to the application, and the automatic extension to 15 June (opens the official IRS page in a new tab) for people abroad moves the filing date, not the payment date.
Take a US citizen employed in Leeds whose British husband has no US connection. Having modelled both statuses, they choose the joint election. Their joint Form 1040 carries the election box, the statement signed by both and a Form W-7 for the husband on the front, with his passport verified by a Certifying Acceptance Agent so it never leaves his hands. The package goes by post to Austin, and the IRS confirms his number on a CP565 notice.
If the decision comes after a separate return has been filed, Publication 519 allows the choice to be made on a joint amended return on Form 1040-X, within three years from filing or two years from payment, whichever is later. The spouse still needs a number for that return. Our individual tax returns work prepares the joint return, the statement and the application together.
When an ITIN expires and how to renew it
An ITIN expires if it is not used on a US federal tax return for three consecutive tax years, at the end of the third year. Renewal is needed only if the number will appear on a federal return again. The IRS says an expired number can still be used on information returns.
This matters to couples who stop filing jointly. Once the election is revoked and the American files separately with NRA for the spouse, the spouse's ITIN falls out of use and lapses. That causes no harm until the spouse needs a US number again, for example for a return of their own.
Renewal uses the same Form W-7 with the renewal box checked, the reason box that applies, and the same document rules. A spouse or dependant renewing to be claimed for a tax benefit must be listed on an attached federal return. A return filed with an expired number is still processed, but the IRS says it may be delayed and some credits refused until the number is renewed.
Our cross-border tax service handles the ITIN alongside the returns that need it. For the spouse's place in the rest of the family's US filing, return to the guide for Americans in the UK.
General information, not advice. The right answer depends on your circumstances and the tax year concerned.
