Getting a US Social Security Number from the UK: A Guide for Accidental Americans
Many Americans in the UK, especially accidental Americans, were never given a Social Security number. Here is why you need one to file a US return and use the Streamlined procedures, and how to apply through the Federal Benefits Unit in London.
Many Americans raised in Britain only learn they need a Social Security number when a bank or tax return asks for one.
Written by the US UK Tax Experts team, cross-border tax specialists
Social Security number from the UK: an introduction
To get a Social Security number from the UK, you apply to the Federal Benefits Unit at the US Embassy in London, using Form SS-5-FS. If you are 12 or older and have never had a number, you must attend a short interview in person. You bring original documents proving your age, US citizenship and identity. Applying is free.
The number matters because the IRS will not give Streamlined penalty relief without one. For the full catch-up programme, read our guide to IRS Streamlined filing. Our Streamlined filing service explains how we prepare the returns once your number arrives.
Why a Social Security number from the UK matters for accidental Americans
An accidental American is someone who holds US citizenship by birth but has lived most or all of their life outside the United States. Many were born in the US to visiting parents, or born in the UK to an American parent. Consequently, few of them were ever given a Social Security number. Our article on the accidental American in the UK explains how people find out about their status. Usually, the first practical step is the number itself.
Why do you need a Social Security number to file US taxes?
You need one because every US tax return must carry a valid taxpayer identification number, and for a US citizen that number is the Social Security number. Without it, you lose access to the Streamlined penalty relief.
The law requires a number on every return
Section 6109 of the Internal Revenue Code says anyone filing a return must include the identifying number the rules prescribe. You can read it at 26 USC 6109 on Cornell LII. The IRS page on taxpayer identification numbers confirms that the Social Security Administration issues SSNs. All other numbers, such as the ITIN, come from the IRS. Meanwhile, the duty to file does not wait for the number. The IRS page for US citizens and resident aliens abroad says citizens are taxed on worldwide income wherever they live.
The Streamlined procedures need a valid SSN
The IRS answers this directly in question 10 of its Streamlined Foreign Offshore questions and answers. If you are eligible for an SSN but do not have one, you may not use the procedures. The IRS may still process returns sent without one, after giving you a temporary IRS number. However, those returns are not eligible for the favourable penalty terms. Therefore, getting your Social Security number from the UK comes before any Streamlined submission.
Why an ITIN is not an option for US citizens
An ITIN is a nine-digit number the IRS issues to people who need a US tax number but are not eligible for an SSN. The IRS ITIN page sets out that rule. Every US citizen is eligible for an SSN, so a citizen cannot use an ITIN instead. The IRS Streamlined procedures page allows an ITIN application with the package only for people ineligible for an SSN. A non-American spouse filing jointly with you is one example.
Other places the number matters
The number also affects credits and banking. For example, the IRS child tax credit page requires each qualifying child to have an SSN valid for employment. It must be issued before the return's due date, including extensions. Additionally, UK banks ask US customers for their number under FATCA, the US law on foreign account reporting. Our article on the FATCA letter from a UK bank covers that request.
Where do you apply for a Social Security number from the UK?
You apply through the Federal Benefits Unit, or FBU, at the US Embassy in London. The FBU is the Social Security Administration's office for people in the UK, and it handles new numbers.
The Federal Benefits Unit in London
The Social Security Administration lists every unit on its foreign country service page, and the United Kingdom entry points to London. The embassy's Federal Benefits Unit page says the unit serves the UK, Bermuda and several African countries. The same page says the unit cannot answer questions about the IRS. So, your tax questions go to the IRS or your adviser, not to the FBU.
Booking the interview
Anyone over 12 applying for a first number must attend in person. The embassy page on Social Security numbers says to request an appointment and name your country of birth. It suggests the subject line "SSN Appointment Required". Appointments are requested by email to FBU.London@ssa.gov, and the FBU confirms by email whether it approves the request. The embassy also warns that bookings through a third-party platform called Picktime are not official.
Notice, hours and phone lines
The two embassy pages differ on notice. The SSN page asks for at least three working days, while the FBU page asks for at least 30 days. The cautious approach is to give 30 days. By appointment, the unit opens Tuesday to Thursday mornings, except US and UK holidays. Importantly, the FBU page says its incoming telephone service ended on 1 October 2026. Contact is now by email, its online form or post.
Applying for a child under 12
Children under 12 do not need an interview. Instead, to get a child a Social Security number from the UK, a parent posts Form SS-5-FS and the original documents to the FBU, at the address on the embassy SSN page. The embassy says it copies the originals and returns them within a few days. It recommends a tracked service, such as Special Delivery, and a prepaid return envelope. Otherwise, documents come back by ordinary post.
What documents do you need for a Social Security number from the UK?
You need evidence of your age, your US citizenship and your identity, plus a completed Form SS-5-FS. If you were born in the US, you also need proof that you lived abroad.
The application form
Form SS-5-FS is the application for a Social Security card used outside the United States. The current version is dated December 2024 and states that applying is free. Every question must be answered and legible. The form also notes that anyone aged 12 or older without a previous number must apply in person.
Evidence of age, citizenship and identity
The rules sit in 20 CFR 422.107, which requires convincing evidence of age, citizenship and true identity. In practice, a US birth certificate proves age and citizenship if you were born in the US. If you were born in the UK, a Consular Report of Birth Abroad, a US passport or a certificate of citizenship can prove citizenship. For identity, the embassy asks for a current, signed passport, either US or foreign. A birth certificate alone never proves identity. If your name has changed, bring the marriage certificate, deed poll or other proof.
Proof you lived outside the United States
People born in the US must also explain why they never received a number. The embassy page on proof of residence outside the United States asks for comprehensive evidence from your departure to today. Suitable records include school reports, old passports, employment records and GP registration. You do not need proof for every year, but gaps can lead to refusal. US-born applicants also complete Form SSA-L706, which lets SSA verify the birth record.
Originals or certified copies only
SSA accepts only originals or copies certified by the office that holds the original record. Form SS-5-FS states that notarised copies and ordinary photocopies are not acceptable. In practice, the London FBU asks for originals at the interview. It also suggests bringing photocopies, which it keeps, and returns the originals to you. Therefore, order replacement certificates early if yours are lost, before you apply for your Social Security number from the UK.
How long does a Social Security number from the UK take?
The embassy says SSN applications take about eight to ten weeks to process. Add the time to collect documents and to secure an appointment, which can be the longer part.
What the embassy says about timing
The eight to ten week figure comes from the embassy's own SSN page. It is an estimate, not a promise. Furthermore, the 30 days' notice for an interview comes on top. If documents are missing, the embassy says you may need a second interview. Consequently, preparing a complete file before you book saves the most time.
What to do while you wait
The wait is not wasted time. You can collect UK bank statements, P60s and pension statements for the years the Streamlined procedures cover. Under the Streamlined Foreign Offshore procedures, that means three years of returns and six years of FBARs. Your adviser can draft the returns and leave the number blank until it arrives. However, nothing should be posted to the IRS before the number arrives.
Why speed still matters
The Streamlined route has conditions that can close it off. The IRS says you cannot use the procedures once it has opened a civil examination of any year. Moreover, your failure to file must have been non-wilful, meaning negligence, mistake or a good faith misunderstanding. A prompt application for your Social Security number from the UK keeps that route open.
What if you plan to give up US citizenship instead?
You do not need an SSN to renounce. Some former citizens can also catch up their taxes without one, under a separate IRS programme.
Renouncing does not require a number
The IRS page on Relief Procedures for Certain Former Citizens is clear on this point. It says obtaining a Social Security number is not a precondition to relinquishing citizenship. However, renouncing is irrevocable and has its own tax rules. Our article on renouncing US citizenship from the UK covers the steps.
The relief procedures without an SSN
The relief procedures are for people who expatriated after 18 March 2010. They need a net worth under $2 million and a total tax liability of $25,000 or less. That liability covers the year of expatriation and the five years before. The IRS FAQ says you can submit without an SSN and need not get one just for this. Even so, if you remain a citizen, the Streamlined route still requires the number.
Common mistakes to avoid
The most common mistake is applying for an ITIN as a citizen. The IRS will not treat it as a valid number for Streamlined. Another mistake is filing before the SSN arrives, which loses the penalty relief. A third is bringing photocopies or notarised copies to the interview. Each of these delays a Social Security number from the UK or the tax filings that depend on it.
A worked example of a Social Security number from the UK
Consider a typical case. Hannah is 34 and was born in Boston while her British parents worked there. The family moved to Leeds when she was two, and she has never lived in the US. Her bank sent a FATCA letter asking for her US tax number. This is an illustrative example, not a real client.
Hannah has never had a Social Security number. She emails the FBU to request an interview, giving 30 days' notice. Meanwhile, she gathers her US birth certificate, her current UK passport, and school, GP and payslip records. She also completes Form SS-5-FS and Form SSA-L706. At the interview, the FBU checks her originals and keeps the photocopies.
What Hannah's case shows
While she waits, Hannah collects three years of P60s and six years of bank statements. Her returns and FBARs are drafted with the number left blank. When the card arrives, the number goes on every form and the Streamlined package is posted. Had she filed first, she would have lost the penalty relief. The order matters: number first, then filing.
How US UK Tax Experts can help
US UK Tax Experts prepares US and UK returns together, from one file, so the two agree. We do not apply for Social Security numbers for anyone, because you apply yourself through the FBU. However, we can tell you what the tax side needs and when. While your application is in progress, we prepare your Streamlined returns and FBARs ready to file. Once your number arrives, we complete and file the package.
Conclusion
For most accidental Americans, a Social Security number from the UK is the first step to getting compliant. The IRS will not grant Streamlined penalty relief without it, and citizens cannot use an ITIN instead. You apply through the Federal Benefits Unit in London, in person if you are 12 or older. Bring originals, give plenty of notice and allow several months in total. Then file, with the number on every return.
Contact us
If you are applying for a Social Security number and need your US returns ready, email hello@usuktaxexperts.com or use our contact form. Tell us how you became a US citizen and which years you have filed. We reply within one working day.
Frequently asked questions
You apply to the Federal Benefits Unit at the US Embassy in London using Form SS-5-FS. If you are 12 or older and have never had a number, you attend a short interview with original documents. Appointments are requested by email.
No, not if you are a US citizen. The IRS says a person eligible for an SSN who does not have one may not use the Streamlined procedures. Returns sent without one may be processed, but without the favourable penalty terms.
No. An ITIN is only for people who need a US tax number but are not eligible for an SSN. Every US citizen is eligible for an SSN, so a citizen must get one.
You need evidence of age, US citizenship and identity, such as a US birth certificate or Consular Report of Birth Abroad and a current signed passport. If you were born in the US, you also need proof you lived abroad. Documents must be originals or copies certified by the issuing office.
The US Embassy says applications take about eight to ten weeks to process. You should add time to gather documents and to get an appointment, as the FBU asks for up to 30 days' notice.
No. Form SS-5-FS states that applying for a Social Security card is free. You may pay for postage, replacement certificates or travel to London.
No. The IRS says obtaining a Social Security number is not a precondition to relinquishing citizenship. Some former citizens can also use the IRS relief procedures without one.
