UK Workplace Pensions and Auto-Enrolment for US Citizens

A UK workplace pension is usually one of the best places a US citizen in Britain can save. Auto-enrolment applies exactly as it does to any UK employee, and Article 18(5) of the US/UK treaty lets a US citizen keep the contributions and the growth out of US tax, within US plan limits. The catch is that the treaty relief has conditions and a ceiling, and the pension still has to be reported to the IRS every year.

This guide is for Americans working for a UK employer, and for dual US/UK citizens who have always lived here. It covers the joining stage: auto-enrolment, contributions and the annual US return. What happens when you eventually draw the money, including the 25% tax-free lump sum, is covered in our guide to how UK pensions are taxed on a US return.

How does auto-enrolment work for a US citizen in the UK?

Auto-enrolment works for a US citizen exactly as it does for a British colleague. GOV.UK says your employer must automatically enrol you if you are aged between 22 and State Pension age, earn at least £10,000 a year and usually work in the UK. Nationality, visa type and US citizenship play no part.

The figures for 2026/27 were confirmed in the government's annual review of the earnings thresholds, which kept all three unchanged from 2025/26:

Auto-enrolment figure	2026/27	What it means
Earnings trigger	£10,000 a year	Earn this and you must be enrolled
Lower limit of qualifying earnings	£6,240 a year	Minimum contributions are worked out on earnings above this
Upper limit of qualifying earnings	£50,270 a year	Minimum contributions stop at this level of earnings
Minimum total contribution	8% of qualifying earnings	At least 3% from the employer; the rest from you, including UK tax relief

The GOV.UK contributions page sets the minimum split as 5% from the employee and 3% from the employer, a total of 8%. Many employers pay more, and many schemes calculate contributions on full salary rather than qualifying earnings. If you earn less than the trigger you can usually ask to join, and your employer cannot refuse.

You can opt out, but GOV.UK explains that you normally get a full refund only if you opt out within one month of being enrolled, and your employer will usually re-enrol you about every three years.

Is a UK workplace pension taxed in the US for a US citizen?

Not while it is building up, provided Article 18(5) of the treaty applies. Without the treaty, the US would treat your employer's contributions as extra wages and your own contributions as coming from taxed salary, and it might tax the investment growth each year. Article 18(5) switches all of that off for a US citizen who meets its conditions.

The treaty text says that contributions paid by or on behalf of the individual during the UK employment "shall be deductible (or excludable) in computing his taxable income in the United States", and that employer contributions and accrued benefits "shall not be treated as part of the employee's taxable income". Article 18 is one of the exceptions to the saving clause in Article 1(5), so the relief protects US citizens, who are otherwise taxed by the US as if the treaty did not exist. Our guide to the saving clause explains why that matters.

The Article 18(5) conditions

Article 18(5) is not automatic. For a US citizen, all of these need to be true:

1. You are resident in the UK for treaty purposes.
2. You exercise an employment in the UK, and the income from it is taxable in the UK.
3. The pay is borne by a UK-resident employer, or by a UK permanent establishment of a foreign employer.
4. The pension scheme is established in the UK, and the contributions are attributable to that UK employment.
5. The relief stays within the cap in Article 18(5)(b), covered in the next section.

An ordinary auto-enrolment scheme run by a UK employer for UK staff normally ticks every box. The awkward cases are set out further down.

How much of a UK workplace pension contribution can a US citizen exclude?

Article 18(5)(b) caps the relief: it "shall not exceed the reliefs that would be allowed by the United States to its residents" for a generally corresponding US pension scheme. For a defined contribution workplace pension, the closest US equivalent is a 401(k), so advisers commonly test contributions against the 401(k) limits for the year.

For 2026, the IRS cost-of-living table sets the employee elective deferral limit at $24,500 and the overall defined contribution limit under section 415(c) at $72,000. The IRS announcement adds an $8,000 catch-up for people aged 50 and over, and $11,250 for those aged 60 to 63. How those limits map onto a UK scheme is a judgement call rather than a bright line, so the method should be chosen once, documented and applied the same way every year.

Most employees paying 5% to 10% of salary are well inside those limits. The cap starts to bite for higher earners making large voluntary contributions, for example using a bonus sacrifice or UK carry-forward. The UK annual allowance for 2026/27 is £60,000, tapering for adjusted income above £260,000, according to HMRC's pension schemes rates. Anything that is relieved in the UK but exceeds the US cap is taxable on the US return, even though HMRC treats it as tax-free.

Salary sacrifice, net pay and relief at source

UK employers deliver tax relief in three ways, and each needs handling on the US return:

• Salary sacrifice. You give up salary and your employer pays the same amount into the pension. Your P60 shows the lower salary. For US purposes the sacrificed amount is generally still a contribution attributable to your employment, so make sure it is counted towards the cap, not ignored. HMRC has announced that from April 2029 only the first £2,000 a year of sacrificed contributions will be free of National Insurance, according to its salary sacrifice guidance. The income tax treatment is unchanged.
• Net pay. Your contribution comes out of gross pay before UK income tax. The P60 figure is after the deduction, so the US return starts from a number that already excludes the contribution.
• Relief at source. You pay from taxed pay and the provider adds basic-rate relief of 20%. Higher-rate taxpayers claim the rest on Self Assessment. For the US return, the gross amount going into the pension, including the top-up, is what is being excluded.

The practical point is that W-2-style wages do not exist in the UK. Your US preparer builds US wages from UK payslips and P60s, and needs to know which method your scheme uses to avoid either double-excluding or never excluding the contribution.

Should a US citizen opt out of a UK workplace pension?

Rarely. A US citizen who opts out gives up the employer contribution, which is free money of at least 3% of qualifying earnings, and loses the one UK savings wrapper that the treaty fully recognises. The main alternatives are worse from a US point of view:

UK savings option	UK tax	US tax for a US citizen
Workplace pension	Tax relief on contributions; growth tax-free	Contributions and growth excluded under Article 18(5), within US limits
Stocks and shares ISA	Tax-free	No treaty protection; income and gains taxable each year; UK funds usually PFICs
Cash ISA	Tax-free	Interest taxable each year; no treaty protection
Ordinary taxed savings	Taxable	Taxable, with foreign tax credit for UK tax

The ISA problem is covered in our guide to ISAs, PFICs and US tax. The short version: a UK fund held in an ISA is a passive foreign investment company, or PFIC, for US purposes, with punitive US tax and extra annual forms. Inside a workplace pension, the same fund is sheltered by Article 18.

There are cases where contributing only the minimum makes sense, such as a short UK stay followed by a move to a country where the pension would be awkward, or when you are already over the US cap. Those are planning decisions, not reasons to opt out by default.

What US reporting does a UK workplace pension trigger?

Treaty relief removes the tax, not the paperwork. A US citizen with a UK workplace pension should expect the following:

• FBAR (FinCEN Form 114). A defined contribution workplace pension is generally reported as a foreign financial account. The FBAR is required when your foreign accounts together exceed $10,000 at any time in the year, per the IRS comparison of Form 8938 and FBAR. See our guide to FBAR versus Form 8938.
• Form 8938. For a single filer living abroad, Form 8938 is needed if specified foreign financial assets exceed $200,000 at the end of the year or $300,000 at any time; the figures double for joint filers. A pension interest is usually included.
• Forms 3520 and 3520-A. Normally not needed for an employer scheme. Revenue Procedure 2020-17 exempts eligible individuals from the foreign trust returns for tax-favoured foreign retirement trusts that meet its conditions. A SIPP is a harder question, covered in our guide to SIPP US tax reporting.
• Form 8833. A treaty-based return position may need disclosure. Our guide to Form 8833 explains when disclosure is required and when it is simply prudent.

Penalties for missing these forms attach to the failure to file, not to any tax owed, so a pension that costs nothing in US tax can still become expensive if it is left off the return.

When does the treaty relief not fit a UK workplace pension?

Most problems come from arrangements that look like an ordinary UK job but miss one of the Article 18(5) conditions:

• Seconded from a US employer. If your salary is borne by a US company with no UK permanent establishment, Article 18(5) does not fit. Article 18(2) and (3) cover people who were already in a pension scheme before moving, but they have their own conditions, including that you were contributing before you started working in the other country.
• Self-employed. Article 18(5) is written for employment. A US citizen contractor paying into a personal pension needs a different analysis; see our page for contractors.
• Using the UK's Foreign Income and Gains regime. Article 18(4) scales relief back where UK tax is charged only on amounts remitted. For most employees paid in the UK this does not arise, but new arrivals should check.
• Moving back to the US. The pot can stay put, and under Article 18(1) growth is generally only taxed in the US when paid out. New contributions from a US job are a different matter and rarely qualify.

Illustrative example: a US citizen employed by a UK company in Manchester earns a salary of about £70,000. The scheme uses salary sacrifice, she sacrifices 6% and the employer pays 8%, all on full salary. Her combined contributions, converted to dollars, sit comfortably within the 2026 US limits. On her US return, the sacrificed salary and the employer's contributions are excluded under Article 18(5), the growth inside the pot is not reported as income, and the pension appears on her FBAR and Form 8938 at its year-end value. Her UK tax on the remaining salary generates foreign tax credits that usually cover the US tax on it. This is illustrative only; the outcome depends on her full circumstances.

What people get wrong with a UK workplace pension as a US citizen

• Reporting the employer's contribution as US wages. This overstates income and wastes foreign tax credits. Article 18(5) excludes it.
• Opting out to "keep things simple". The employer match is lost, and the savings usually end up in an ISA, which is worse for US tax.
• Leaving the pension off the FBAR. No tax is due does not mean no reporting is due.
• Ignoring the US cap. Large one-off contributions from a bonus can exceed what a comparable US plan would allow, and the excess is taxable in the US.
• Assuming it all works the same after a move. Growth stays protected, but contributions from a non-UK job usually are not.
• Forgetting when you can draw. The normal minimum pension age rises from 55 to 57 from 6 April 2028, which affects long-term plans for Americans intending to retire in the US.

Getting the UK workplace pension right from year one

The easiest time to get a UK workplace pension right is the first US return after you join. The decisions made then, how contributions are excluded, how the cap is tested and how the pension is reported, carry forward for decades and shape what happens at retirement. Later, when you draw on the pension, the questions change to where you live, lump sums and foreign tax credits, which our guide to drawing US and UK pensions at the same time covers.

US/UK Cross Border Tax — US CPAs and UK tax advisers working as one team; London, Manchester, New York, San Francisco. Our UK workplace pension advice for US citizens sits within our US/UK pensions service, alongside treaty relief claims and US tax returns for Americans in the UK. If you want your workplace pension set up correctly on both sides, get in touch.