Does my UK spouse need an ITIN if I file married filing separately?

Usually not. Where you file married filing separately and your British spouse does not have and is not required to have a Social Security number or an ITIN, the Instructions for Form 1040 direct you to enter NRA in the space for the spouse's Social Security number. Your spouse is identified without being brought into the US tax system. A number becomes necessary only if you file jointly, claim your spouse for an allowable tax benefit, or your spouse has a US filing obligation of their own - US rental income or a US property disposal being the usual triggers.

How do I get an ITIN from the UK without sending my original passport to the IRS?

Use an IRS Certifying Acceptance Agent. A CAA is authorised under the IRS Acceptance Agent Program to examine your original passport, certify it, and forward the certification instead of the document, returning the passport to you immediately. The Instructions for Form W-7 confirm that a CAA can verify originals and issuing-agency certified copies for primary and secondary applicants and their dependants, excluding foreign military identification cards. Note the limit for dependants: a CAA can only verify passports and birth certificates, so any other dependant document must still be posted to Austin.

Yes. The IRS ITIN expiration guidance states that if an ITIN is not used on a US federal tax return for any three consecutive tax years, it expires on 31 December after the third tax year of non-use. The IRS also ran a scheduled middle-digit expiry programme between 2016 and 2020 that retired ITINs issued before 2013 unless they were renewed. The most common cause of expiry in UK households is a perfectly sensible switch from joint filing to married filing separately, which leaves the spouse's number unused for three years without anyone noticing.

What happens if I file a US return with an expired ITIN?

The return is still processed, but badly. The IRS ITIN expiration guidance states that there may be a delay in processing, that certain credits may not be claimable unless the ITIN is renewed, and that this may result in a reduced refund or in penalties and interest. In practice the number fails validation, whatever was attached to that person falls out of the computation, and interest runs on the resulting balance until the number is renewed and the position corrected. Renewing before you file is always cheaper than renewing afterwards.

Can I apply for an ITIN without attaching a tax return?

Only under one of the five Exceptions in the Instructions for Form W-7. Exception 1 covers passive income subject to third-party withholding or a treaty claim, Exception 2 wages, scholarships and gambling income, Exception 3 mortgage interest subject to third-party reporting, Exception 4 dispositions of US real property interests by foreign persons, and Exception 5 non-US representatives of foreign corporations under T.D. 9363. For UK households Exception 4 matters most - a British spouse selling US property needs the number for the FIRPTA withholding paperwork long before any return falls due.

Should I elect to treat my British spouse as a US resident so we can file jointly?

For most wealthy UK households, no. The election under IRC section 6013(g) requires a statement signed by both spouses attached to the first joint return, and the IRS is clear that each spouse must then report their entire worldwide income for that year and every later year. For a British spouse holding UK funds that means PFIC reporting on Form 8621, the loss of ISA treatment for US purposes, and specified individual status for Form 8938 - the Instructions for Form 8938 expressly cover an electing non-resident alien spouse. It is also effectively irreversible: once ended, neither spouse can make the choice again in any later tax year.

US UK Tax Returns Preparation: ITIN for a Non-US Spouse

US UK tax returns preparation for an American living in London runs into the same obstacle in almost every household: a British spouse or child who must be identified on a US federal return but cannot get a Social Security number. The answer is an Individual Taxpayer Identification Number. An ITIN is a nine-digit number the IRS issues, in the words of the IRS Individual Taxpayer Identification Number page, where you need a US taxpayer identification number for federal tax purposes but are not eligible for a Social Security number. You apply on Form W-7, you normally attach it to the return it supports, you prove identity with original documents or copies certified by the issuing agency, and - the point that catches out more filers than any other - the number expires if it is not used on a US federal return for three consecutive tax years.

For a wealthy household the better question is not how to obtain an ITIN but whether the spouse needs one at all, and what accepting one commits the family to. The number itself is harmless. The filing position that usually travels with it - electing to treat a non-resident alien spouse as a US resident - is not, and for a British spouse holding a substantial UK portfolio it is often the most expensive box anyone ticks on a US return.

What is an ITIN, and who actually needs one?

An ITIN is a tax processing number and nothing else. The IRS is blunt about its limits: it authorises nobody to work in the United States, confers no immigration status, and does not qualify the holder for Social Security benefits or the Earned Income Tax Credit. It exists because IRC section 6109 requires a taxpayer identifying number on a return, and somebody has to be identifiable when a US return names them.

The people who need one are people who must appear on a US federal return and cannot obtain an SSN. Form W-7 asks the applicant to tick a reason code running from (a) to (h). For a UK household two matter: code (e), covering a resident or non-resident alien spouse claimed for an allowable tax benefit or electing to file jointly with a spouse who is a US citizen or resident alien, and code (d), covering a dependant. The remaining codes deal with treaty claimants, non-resident aliens filing their own returns, and students and researchers on US visas.

There is a gate in front of both codes that is easy to miss and fatal to ignore. The Instructions for Form W-7 on IRS.gov state that spouses and dependants are not eligible for an ITIN, or to renew one, unless they are claimed for an allowable tax benefit or they file their own tax return. The IRS defines those allowable benefits as a spouse filing a joint return, head of household, qualifying surviving spouse, the American opportunity tax credit, the premium tax credit, the child and dependent care credit, and the credit for other dependents. If none applies and the spouse has no US filing obligation of their own, there is nothing for the IRS to issue a number against - and the rejection arrives months later.

An ITIN does not authorise work in the United States and grants no immigration status.
It does not entitle the holder to Social Security benefits or the Earned Income Tax Credit.
It is not a banking identity and not a substitute for a National Insurance number.
It is issued only where a genuine US federal tax purpose sits behind it.
Once an SSN is issued the ITIN must stop being used, and the IRS will not issue an ITIN to anyone who already holds an SSN.

Does my British spouse actually need an ITIN?

The answer is decided by filing status, not by the marriage. A US citizen in London who files married filing separately, and whose British spouse has no US income, no US assets and no US filing obligation, generally needs no number for that spouse. The Instructions for Form 1040 deal with the point directly: where the spouse does not have and is not required to have an SSN or ITIN, the filer enters NRA in the space for the spouse's Social Security number. The spouse is identified on the return without ever entering the US tax system.

The moment the return does more than name the spouse, a number becomes necessary. A joint return requires one, because it treats the British spouse as a taxpayer on that return. Claiming the spouse for any allowable benefit requires one. And if the spouse has a US filing obligation in their own right - US-source dividends outside treaty withholding, rental income from a US property, or a disposal of US real estate that brings FIRPTA withholding into play - the spouse needs an ITIN whether or not the American spouse wants one issued.

We therefore treat the ITIN question and the filing status question as one decision rather than two. Advisers who obtain the number first and consider status afterwards routinely leave a British spouse with a US taxpayer identification number, a US filing footprint and nothing to show for either.

Required if you file a joint US return with your British spouse.
Required if your spouse must file a US return of their own, for example on US rental income or a US property disposal.
Required for any dependant claimed for an allowable tax benefit who cannot obtain a Social Security number.
Not required merely because you are married to a UK national.
Not required where you file married filing separately and your spouse has no US filing obligation - you enter NRA in the spouse's number field instead.

The Form W-7 process in US UK tax returns preparation

Form W-7, Application for IRS Individual Taxpayer Identification Number, is a single page with a demanding instruction booklet behind it. The current revision is December 2024, and the Instructions for Form W-7 (12/2024) on IRS.gov are the governing text. The applicant ticks new application or renewal, ticks the reason code, and completes name, mailing address, foreign address, date and place of birth, countries of citizenship, foreign tax identification number where one exists - for a British spouse, a Unique Taxpayer Reference if HMRC has issued one - and any US visa details.

The name entered on line 1a must match the identifying document exactly. This sounds trivial and is not. A British wife whose passport carries her maiden name, whose marriage certificate carries her married name, and whose US return carries a third variant will have the package returned. Where the name has changed since an earlier ITIN was issued, the IRS asks for supporting evidence such as a marriage certificate or a court order. The applicant signs personally; a parent or court-appointed guardian may sign for a child under 18, entering their own name and the relationship.

The W-7, the identity evidence and the tax return travel as one paper package. Form W-7 cannot be filed electronically, and a return cannot be e-filed using an ITIN in the calendar year the ITIN is assigned. The package goes to Internal Revenue Service, ITIN Operation, P.O. Box 149342, Austin, TX 78714-9342, or by private delivery service to ITIN Operation, Mail Stop 6090-AUSC, 3651 S. Interregional Hwy 35, Austin, TX 78741-0000. The IRS asks you to allow seven weeks for notification of the outcome, and nine to eleven weeks where the application is submitted in the peak period from 15 January to 30 April or from overseas. A London household is, by definition, always in the longer window.

Which identifying documents does the IRS accept?

The Instructions for Form W-7 contain a table of thirteen acceptable documents. A valid passport is the only stand-alone item on it: submit an original valid passport or a certified copy from the issuing agency and nothing further from the table is required. Every other document must be paired with a second, one of which must carry a photograph where the applicant is aged 14 or over.

Passport - the only stand-alone document.
USCIS photo identification.
Visa issued by the US Department of State.
US driver's licence.
US military identification card.
Foreign driver's licence.
Foreign military identification card.
National identification card.
US state identification card.
Foreign voter's registration card.
Civil birth certificate.
Medical records - dependants under age 6 only.
School records - dependants under age 24 only.

The critical sentence sits underneath the table. The IRS requires original documents, or certified copies of those documents from the issuing agency, and defines a certified copy as one the original issuing agency provides and certifies as an exact copy, carrying that agency's official stamped seal. Read that against the British reality. The issuing agency for a British passport is HM Passport Office. It is not a UK notary public, not a solicitor, not a bank manager, and not a US embassy stamping a photocopy. Certification by anyone other than the body that issued the document fails the IRS definition, which is why so many carefully notarised UK packages come back unprocessed. Anyone intending to rely on an agency-certified copy should confirm the availability of that service before building a filing timetable around it.

How do I get an ITIN from the UK without posting my passport?

There are three routes, and for a client who travels constantly only one of them is realistic.

The first is to post the original passport, or an agency-certified copy of it, to the ITIN Operation in Austin with the rest of the package. The IRS does return original documents, but the round trip runs to months, it crosses the Atlantic twice in the ordinary post, and it is unworkable for someone who flies to New York, Zurich and Dubai in a normal quarter. It can be sensible for a document nobody needs day to day. It is rarely right for a primary passport.

The second route solves the problem: a Certifying Acceptance Agent. A CAA is authorised by the IRS under its Acceptance Agent Program to examine the original document, certify it, and send the certification rather than the document itself. The Instructions for Form W-7 set the scope precisely - a CAA can verify original documentation and issuing-agency certified copies for primary and secondary applicants and their dependants, excluding foreign military identification cards, and the documentation is returned immediately. The IRS publishes a list of Acceptance Agents by location, and the United Kingdom is well represented, with a concentration in London.

There is a limit inside that scope that almost no guide mentions. For dependants, a CAA can only verify passports and birth certificates. If a child's evidence runs to school records, medical records or a state identification card, those documents must still travel to Austin in original form. A family package can therefore succeed for the spouse and stall for a child, which is the strongest practical argument for making sure every dependant holds a current British passport before an application is started.

The third route is an IRS Taxpayer Assistance Center, which verifies originals and certified copies and hands them straight back, by appointment only - but the IRS frames this as something done while in the United States, and its guidance on obtaining an ITIN from abroad offers no overseas IRS counter. The instructions do note that you may be able to request a certified copy of documents at an embassy or consulate, while warning that services vary between countries and that the relevant post should be contacted first. That is a genuine option in some jurisdictions. It is not a dependable one for a British passport, because a consulate is not the issuing agency.

Post the original passport or an agency-certified copy to the ITIN Operation in Austin, Texas, and be without it for months.
Use an IRS Certifying Acceptance Agent, who verifies the document and returns it immediately, subject to the passport and birth certificate limit for dependants.
Attend an IRS Taxpayer Assistance Center by appointment while in the United States, or explore an embassy or consulate certified copy where that service exists.

Does Form W-7 have to be filed with a tax return?

Normally, yes. The default rule is that Form W-7 is attached to the valid US federal income tax return for which the number is needed, and the two are processed together: the IRS assigns the ITIN, writes it onto the return, and then processes the return. You do not file the return separately, and you do not file the W-7 on its own hoping to use the number later.

The Instructions for Form W-7 set out five Exceptions where no return is attached. Exception 1 covers passive income subject to third-party withholding or a treaty claim. Exception 2 covers wages, scholarships and gambling income. Exception 3 covers mortgage interest subject to third-party reporting. Exception 4 covers dispositions of US real property interests by foreign persons. Exception 5 covers non-US representatives of foreign corporations under T.D. 9363. Each Exception carries its own documentary requirements, and the IRS applies them strictly.

For a London household, Exceptions one, three and four are the ones that bite. A British spouse receiving US-source dividends where a treaty rate is claimed sits inside Exception 1. A couple who own a US property with a US mortgage may reach Exception 3. A British spouse selling US property, where FIRPTA withholding applies and a withholding certificate on Form 8288-B is in play, falls within Exception 4 - and there the number is needed urgently rather than at the filing deadline, because the withholding agent cannot complete the paperwork without it.

Timing deserves a word. The IRS expects the package on or before the due date for the return, and warns that failure to file the return in time with a complete Form W-7 and the required documentation may result in the denial of refundable credits. Where the number will not be ready in time, the correct answer is an extension on Form 4868, not a rushed or incomplete W-7. Because the first-year package is a paper package, send it by a tracked route and retain proof of despatch - there is no electronic acknowledgement to fall back on.

Do ITINs expire, and how do I renew one?

Yes, and this is the single most commonly missed point in the whole subject. The IRS ITIN expiration guidance states that if an ITIN is not used on a US federal tax return for any three consecutive tax years, it expires on 31 December after the third tax year of non-use. The Instructions for Form W-7 put the same rule the other way round: if the number was not included on at least one US federal tax return for the last three consecutive tax years, it expires on 31 December of the third consecutive tax year and must be renewed before it can be used again. Separately, the IRS ran a scheduled middle-digit expiry programme between 2016 and 2020 which retired ITINs issued before 2013 unless they were renewed at the time.

Here is the trap, and good planning creates it rather than bad. The commonest reason a British spouse's ITIN goes three years without appearing on a return is that the couple sensibly stopped filing jointly and moved to married filing separately. The number then sits unused, expires on a 31 December nobody noted, and resurfaces years later when the family sells a US property, needs a withholding certificate, or decides to file jointly again for a year with an unusual income profile. The IRS may issue a CP48 notice warning that renewal is due, but that notice goes to the last address it holds, and international addresses go stale.

Filing with an expired number does not stop the return being processed. It makes the processing worse. The IRS ITIN expiration guidance is explicit that there may be a delay in processing the return, that certain credits may not be claimable unless the ITIN is renewed, and that this may result in a reduced refund or in penalties and interest. The return goes in, the number fails validation, whatever attaches to that person falls out of the computation, and interest runs while the balance moves against you. Once the number is renewed the position can be restored, but a year has usually gone by.

Renewal itself is straightforward when it is done deliberately. An ITIN only needs renewing if it is going to appear on a US federal return. You complete Form W-7, tick Renew an existing ITIN in the application type box, give the reason code again, and complete lines 6e and 6f with the existing number and the name under which it was issued. Identity evidence is required exactly as it was for the original application, so the CAA route applies to renewals too. A plain renewal does not need a return attached - but the IRS is clear that spouses and dependants renewing in order to be claimed for an allowable tax benefit must be listed on an attached US federal tax return, together with the schedule or form supporting that benefit.

Diarise the expiry date the moment a household stops filing jointly - three consecutive unused tax years is the trigger.
Check the number before any US property transaction, not after the buyer's agent asks for it.
Keep the IRS address current so a CP48 notice actually arrives.
Renew before filing rather than with the filing, wherever the timetable allows.
Remember that a renewal needs the same identity evidence as a first application.

Should we elect to treat a British spouse as a US resident?

Here the ITIN stops being administration and becomes a decision with a price tag. IRC section 6013(g) allows a US citizen or resident married to a non-resident alien to elect to treat that spouse as a US resident for income tax purposes, which is what makes a joint return possible; IRC section 6013(h) does the equivalent job where a spouse is a dual-status alien for the year. The IRS nonresident spouse page sets out the mechanics: a statement signed by both spouses is attached to the joint return for the first year the choice applies, and the spouse must hold either an SSN or an ITIN - which is usually why the W-7 is on the desk at all.

The consequence is stated on the same page and it is total. Each spouse must report their entire worldwide income for the year the choice is made and for all later years, unless the choice is ended or suspended. For a British spouse with a modest income that can be a fair trade for wider bands. For the readership of this site it usually is not. A British spouse with a UK investment portfolio, UK dividend income, UK capital gains and let property is being invited to move all of it onto a US return, where UK tax treatment stops being the answer and US rules take over.

Three exposures follow, and they are why we so often advise against the election. First, UK funds - OEICs and comparable collective vehicles, and investment companies - are generally passive foreign investment companies for US purposes, which drags Form 8621 and a punitive default regime onto the return. Second, an ISA is not a tax-free wrapper in American eyes; the income and gains inside it become reportable. Third, and almost nobody flags this at the outset, the Instructions for Form 8938 define a specified individual to include a non-resident alien who elects to be treated as a resident alien for the purpose of filing a joint income tax return. The election therefore does not merely add income to a return; it brings the British spouse's own accounts and holdings into US information reporting, with the penalty exposure that accompanies it.

One further point makes this a one-shot decision. The election ends on revocation by either spouse, on the death of either spouse, on legal separation, or on inadequate records. The IRS then states that once the choice has ended for any of those reasons, neither spouse can make the choice in any later tax year - it is a once-in-a-lifetime choice. A couple who elect, dislike the outcome and revoke have not returned to the starting line; they have closed the door permanently. That asymmetry alone justifies modelling both filing positions properly before anyone signs the statement.

Dependants: British children and what the IRS expects

Start with a question that saves several families a wasted application every year: is the child actually a US citizen? A child born in London to a US citizen parent will very often have acquired US citizenship at birth. That child does not need an ITIN. That child needs a Consular Report of Birth Abroad and a Social Security number, and the IRS will not issue an ITIN to anyone eligible for an SSN. The ITIN question arises for the genuinely non-US child, most often a British stepchild or a child of a British spouse from an earlier relationship.

Where an ITIN is right, the dependant faces the eligibility gate described earlier and a residency substantiation requirement on top of it. A passport carrying a US date-of-entry stamp settles the residency question on its own. Without one, the IRS looks for specific US-connected evidence by age band, and it is unforgiving about the age cut-offs. Only dependants of US military personnel stationed overseas, and applicants from Canada or Mexico claimed for an allowable benefit other than the credit for other dependents, escape the residency requirement altogether - a UK-resident child does not.

Under age 6 - a US medical record, US school record, US state identification card or US visa.
Age 6 to 17 - a US school record, US state identification card, US driver's licence or US visa.
Age 18 and over - a US school record (under age 24 only), US state identification card, US driver's licence, US visa, US bank statement, US rental statement or US utility bill.
A passport bearing a US date-of-entry stamp removes the need for any of the above.
Relationship evidence is expected as well, which for a spouse means the marriage record and for a child usually means a civil birth certificate.

A worked example: an American banker in London with a British wife

Marcus Ellery is a US citizen and a managing director at an investment bank in the City. He has lived in Kensington for eleven years, earns a substantial salary and bonus in pounds, and files a US return each year alongside his UK position. His wife Philippa is British, has never held a green card, has never spent a meaningful period in the United States, and has her own money: a UK share and fund portfolio of some size, a maturing ISA, a let property in Somerset, and directors' fees from a family company. Their two children were born in London, are US citizens through Marcus, and already hold Social Security numbers.

The previous adviser proposed obtaining an ITIN for Philippa and filing jointly, on the reasoning that joint bands are wider. Run properly, that reasoning collapses. The section 6013(g) election would put Philippa's entire worldwide income onto a US return - the Somerset rental, the UK dividends, the directors' fees, the gains in the portfolio. Her UK fund holdings would become PFICs requiring Form 8621. The ISA would lose its character. She would become a specified individual for Form 8938, so her personal UK accounts would be reported to the IRS. The band advantage on Marcus's income is real but modest; the compliance cost, the PFIC exposure and the permanent loss of a once-in-a-lifetime election are not.

The position we filed instead was married filing separately, with NRA entered in the space for Philippa's Social Security number. She needed no ITIN, no US filing footprint and no W-7. Two years later the couple bought a US property jointly, at which point she did need a number - obtained on Form W-7 under an Exception, with her British passport verified by a Certifying Acceptance Agent in London so that it never left her possession. The number now appears on a US return in each year the property produces income, which keeps it alive and clear of the three-year expiry rule. The sequencing was the whole of the value.

Practical sequencing and the errors we see most

Most ITIN failures are failures of order rather than of understanding. The sequence that works is: establish whether the spouse has a US filing obligation of their own; model both filing statuses with the UK income included; only then decide whether a number is needed; then choose the verification route; and only then prepare the W-7 alongside the return it will be attached to. Reverse any two of those steps and the package is either rejected or achieves something nobody wanted.

Sound US UK tax returns preparation also means treating an ITIN as a live asset rather than a one-off task. It carries an expiry condition, it is tied to a name that can change, and it is tied to an address the IRS will use to warn you. All three drift over a decade of expatriate life, and all three are cheap to maintain and expensive to repair.

Applying for an ITIN before the filing status is decided, creating a US footprint with nothing to show for it.
Sending a copy certified by a notary or solicitor rather than by the issuing agency, and having the package returned.
Assuming a Certifying Acceptance Agent can verify every document for a child, when the scope for dependants is limited to passports and birth certificates.
Letting the number lapse after a switch from a joint return to separate returns, then discovering it at the point of a US property sale.
Making the section 6013(g) election without pricing the PFIC and Form 8938 consequences, and without appreciating that revoking it closes the door permanently.
Filing the return and the Form W-7 separately, or attempting to e-file a return using an ITIN in the year it is assigned.

An ITIN is a small administrative object attached to a large strategic question. Obtained at the right moment, verified through a Certifying Acceptance Agent so that a passport never leaves the country, and kept alive on a return each year, it is a non-event. Obtained reflexively, alongside an election nobody modelled, it can move a British spouse's entire financial life into the US tax and reporting system for good. The form takes an afternoon; the decision behind it deserves considerably longer.