National Insurance for Americans in the UK: What You Pay and What It Buys

National Insurance for Americans in the UK works like this: if you are employed by a UK employer or self-employed while living in Britain, you pay UK National Insurance, not US Social Security tax. If a US employer sends you to the UK temporarily, you can stay in US Social Security for up to about five years with a certificate of coverage. The contributions build a UK State Pension record, but they do not reduce your US tax bill.

National Insurance is the UK's social security tax. It funds the State Pension and some other benefits, and it is collected separately from income tax even though both come off the same payslip. Americans moving to Britain often treat it as a line item to ignore. That is a mistake in both directions: some people pay it when a US certificate would have kept them out, and others assume their US employer has dealt with it when nobody applied for the certificate at all.

This guide covers the 2026/27 rates, the US-UK totalization agreement (the treaty that decides which country's system you belong to), the US tax treatment, and what your National Insurance record is worth when you retire. Figures below are for the UK tax year 6 April 2026 to 5 April 2027 and come from GOV.UK and the Social Security Administration, linked as they appear.

Do Americans in the UK pay National Insurance?

Yes, most Americans who work in the UK pay National Insurance. Nationality is irrelevant: liability follows where you work and who employs you. An American hired by a UK company, or self-employed while living in the UK, is inside the UK system from the start.

The US-UK totalization agreement is what stops the same earnings being charged to both countries. The Social Security Administration's guide to the agreement with the United Kingdom explains that each period of work is assigned to one country's system. The general rule is that you are covered where you physically work. The detached-worker rule and the self-employed rule, covered below, are the two exceptions Americans run into most.

The National Insurance number

You need a National Insurance number so your contributions are recorded against your name. GOV.UK's National Insurance number page says you can apply online if you live in the UK, have the right to work and are working, looking for work or have a job offer. You can only apply from inside the UK, and you can start work before the number arrives if you can prove your right to work.

The National Insurance number is not the same as a Unique Taxpayer Reference. If you also need to file a Self Assessment return, our guide to the UTR number for Americans in the UK explains the second identifier.

National Insurance rates for Americans in the UK in 2026/27

The class of National Insurance you pay depends on whether you are an employee or self-employed. The table below summarises the 2026/27 figures published on GOV.UK in Rates and thresholds for employers 2026 to 2027 and Self-employed National Insurance rates.

Class	Who pays	2026/27 rate and threshold
Class 1 (employee)	Employees, through PAYE	0% up to £12,570 a year (Primary Threshold); 8% from £12,570 to £50,270 (Upper Earnings Limit); 2% above £50,270
Class 1 (employer)	The UK employer, on top of salary	15% above the Secondary Threshold of £5,000 a year
Class 4	Self-employed, through Self Assessment	6% on profits from £12,570 to £50,270; 2% above £50,270
Class 2	Self-employed with low profits (voluntary)	Treated as paid if profits are £7,105 or more; voluntary £3.65 a week below that
Class 3	Anyone filling gaps in their record (voluntary)	£18.40 a week

Employee National Insurance is worked out on each pay period, not on the year as a whole, so a bonus month can carry more National Insurance than an annual calculation suggests. Unlike income tax, Class 1 National Insurance stops when you reach State Pension age.

Illustrative example: a US citizen takes a permanent job with a London employer at a salary of £60,000 for 2026/27, paid evenly through the year. The Class 1 employee National Insurance is 8% of £37,700 (£50,270 minus £12,570), which is £3,016, plus 2% of £9,730 (£60,000 minus £50,270), which is £194.60: £3,210.60 in total. The employer separately pays 15% of £55,000 (£60,000 minus £5,000), which is £8,250, before any employment allowance. The employee pays no US Social Security tax on this salary, because the work is UK employment under the totalization agreement.

Can a US employer keep you in US Social Security?

Yes, for a temporary assignment. The Social Security Administration's annotation of Article 4.2 of the US-UK agreement says an employee of a US employer who is temporarily transferred to work in the UK for the same employer, or an affiliate, stays covered by US Social Security. Ordinarily that applies only if the UK work does not exceed 5 years, and the competent authorities can agree an extension.

Two conditions are easy to miss. First, the employee should normally have been working for the sending employer in the US immediately before the transfer, so someone hired in London by a US company does not qualify. Second, the exemption is not automatic: the employer has to obtain a certificate of coverage from the Social Security Administration, which the employee gives to the UK employer or payroll so National Insurance is not deducted.

Employee or self-employed: which system covers you

Your situation	Covered by	What you need
Hired directly by a UK employer	UK National Insurance	A National Insurance number
Sent to the UK by your US employer, expected to last 5 years or less	US Social Security (FICA)	A US certificate of coverage, obtained by the employer
US assignment that runs past 5 years with no extension	UK National Insurance from that point	Payroll changes to UK National Insurance
Self-employed and living in the UK	UK National Insurance (Class 2 and Class 4)	A UK statement to support the US self-employment tax exemption
Self-employed and living in the US, with UK clients	US self-employment tax	A US certificate of coverage, if asked to prove it

The self-employed rule follows residence. The Social Security Administration states that self-employed workers who reside in the United Kingdom are assigned UK coverage. For a UK-resident American freelancer that means Class 4 through Self Assessment, and no US self-employment tax, provided the exemption is claimed properly on the US return (see below). Our guide to Self Assessment for self-employed Americans in the UK covers the UK filing side.

How National Insurance interacts with your US tax return

UK National Insurance changes your US return in three ways, and the first one surprises most people.

1. National Insurance is not creditable against US tax

IRS Publication 514 states that no deduction or credit is allowed for social security taxes paid or accrued to a foreign country with which the United States has a social security agreement. The UK has such an agreement, so National Insurance cannot go on Form 1116 and cannot be deducted. Only UK income tax counts towards the foreign tax credit. When you compare a UK payslip to a US one, remember that the National Insurance line is a pure UK cost.

2. Self-employed Americans must claim the US exemption

A UK-resident self-employed American does not pay US self-employment tax on earnings covered by UK National Insurance, but the IRS does not know that unless you tell it. The Instructions for Schedule SE say to get a statement from the foreign country's social security agency confirming coverage, not to complete Schedule SE, to attach a copy of the statement to the return, and to check box 3 on Schedule 2 (Form 1040), line 4, writing "Exempt, see attached statement". Missing this step is a common reason for an unexpected US self-employment tax bill.

3. Seconded employees keep paying FICA

An employee who stays in US Social Security under a certificate of coverage continues to have FICA withheld by the US employer, and pays no UK National Insurance on the same earnings. Income tax is a separate question: the same person may still owe UK income tax and need a UK return. Our guide to tax obligations for Americans living in the UK sets out both sides.

What does National Insurance buy you?

National Insurance mainly buys a UK State Pension. GOV.UK says you need 10 qualifying years on your record to get any new State Pension, and if your record started after April 2016 you need 35 qualifying years for the full rate. GOV.UK gives the full rate of new State Pension as £241.30 a week, the 2026/27 rate.

Combining US and UK work history

The totalization agreement also lets you combine periods. If you do not have enough UK years for a UK State Pension, or enough US credits for US Social Security, the agreement allows periods in the other country to be counted towards eligibility. Each country then pays a benefit based on the contributions actually made to it. A short UK career is therefore rarely wasted.

One worry has gone away. The Social Security Administration says the Social Security Fairness Act, signed on 5 January 2025, repealed the Windfall Elimination Provision and the Government Pension Offset, which no longer apply to benefits payable for January 2024 and later. How each pension is taxed is a separate treaty question, covered in our guide to the UK State Pension and US Social Security.

Voluntary National Insurance after you leave the UK

Many Americans leave the UK a few years short of 10 qualifying years and want to keep building the record from the US. The rules changed on 6 April 2026. GOV.UK's page on voluntary contributions if you live or work abroad says:

• You can no longer pay voluntary Class 2 contributions for time abroad. Class 3, at £18.40 a week for 2026/27, is the only option.
• To pay Class 3 for time abroad after 5 April 2026, you must either have lived in the UK for 10 years in a row or have 10 years of qualifying contributions in total. Voluntary contributions for other periods abroad, and National Insurance credits, do not count towards those 10 years.
• You apply on form CF83.
• Transitional rules can keep the old three-year test for people who applied for 2024/25 or 2025/26 on or before 5 April 2026 and meet the payment and application dates GOV.UK sets out.

For a typical American who spent five or six years in London, the new 10-year test usually means voluntary contributions from abroad are no longer available. Before you leave, check your record on GOV.UK and consider whether to fill gaps in years you were UK resident while that is still possible.

What people get wrong about National Insurance

1. Assuming a US employer handles it. A US company sending you to London must apply for the certificate of coverage. If nobody does, UK payroll should deduct National Insurance and the US employer may still withhold FICA, so you pay twice until it is fixed.
2. Treating a local UK hire as a secondment. If you were recruited in the UK, the detached-worker rule does not apply, whatever the employer's nationality.
3. Missing the 5-year limit. Assignments drift. When the expected period passes 5 years without an agreed extension, coverage normally switches to the UK.
4. Claiming National Insurance on Form 1116. It is not creditable. Including it overstates the foreign tax credit.
5. Paying US self-employment tax while living in the UK. A UK-resident freelancer is covered by UK National Insurance; the US exemption needs the statement attached to the return.
6. Leaving without checking the record. Since 6 April 2026, voluntary contributions from abroad need 10 years of UK residence or contributions, so gaps are harder to fix later.

Getting National Insurance right from day one

National Insurance is one of the few cross-border costs that can be settled before the first payslip: confirm whether you are a local hire or a secondee, get the certificate of coverage in place if you are seconded, and make sure your US return reflects whichever system covers you. Our National Insurance and tax advice for Americans in the UK covers payroll set-up, certificate questions and the US and UK returns together. For retirement planning across both systems, see our US-UK pensions service, and for the UK return itself, our UK Self Assessment service.

US/UK Cross Border Tax is US CPAs and UK tax advisers working as one team, with offices in London, Manchester, New York and San Francisco. If you are starting a UK job, being seconded from the US, or planning to leave Britain, contact us to check your National Insurance position before it becomes a refund claim.