Why a Salary Sacrifice Pension Looks Different From Washington
A salary sacrifice pension is the most efficient way for a high earner on UK payroll to fund retirement, because the sacrificed pay escapes income tax and National Insurance in one move. However, if you hold a US passport, Britain's generosity is only half the story. The IRS does not recognise a UK registered pension scheme as a qualified plan, so every pound you sacrifice becomes an employer contribution to a foreign scheme, and American law taxes that by default. Consequently, the only thing standing between you and US tax on money you cannot touch is Article 18(5) of the US-UK tax treaty, and that article comes with a ceiling most British payroll teams have never heard of.
At TaxYork, we prepare US and UK returns for bankers, partners, founders and senior executives who sacrifice five- and six-figure sums every year. In our experience, the UK side is almost always right and the US side is almost always guessed. This guide therefore explains, with 2026 figures, exactly how the IRS treats your salary sacrifice pension, where the treaty stops, what happens to bonus sacrifice, how the April 2029 National Insurance cap changes the maths, and how to report it all correctly.
How a Salary Sacrifice Pension Works in the UK
Under a salary sacrifice pension arrangement, you agree a contractual reduction in your gross pay and your employer pays an equal amount into your pension. Because the contribution comes from the employer, it never passes through PAYE. As a result, you save income tax at your marginal rate and employee National Insurance, while your employer saves its 15% secondary contribution. HMRC's own guidance on salary sacrifice and the effects on PAYE confirms that the reduction must be a genuine change to your contractual entitlement, agreed before the pay is earned.
For a 45% taxpayer, the saving from a salary sacrifice pension is substantial. Every £10,000 sacrificed saves £4,500 of income tax and £200 of employee National Insurance at the 2% rate above the upper earnings limit. Furthermore, many employers pass some or all of their £1,500 National Insurance saving back into your pension. Additionally, sacrifice sits comfortably inside the UK annual allowance of £60,000, subject to the taper for the highest earners.
Why the US Starts From a Different Place
The US tax code does not care what HMRC calls your contribution. Instead, it asks two questions. First, did you give up the pay before you earned it? Second, what kind of arrangement received the money? On the first question, the IRS generally respects a genuine, prospective and irrevocable reduction, so the sacrificed amount is not treated as cash wages through the doctrine of constructive receipt. On the second question, however, the answer is unfavourable.
A UK registered pension scheme does not meet section 401(a) of the Internal Revenue Code. Consequently, the IRS generally treats it as a non-exempt employees' trust under section 402(b). Under that regime, employer contributions are taxable to you as soon as they vest, which for a UK defined contribution scheme is usually immediately. In short, without the treaty, your salary sacrifice pension contribution is simply taxable US compensation paid into an account you cannot access for decades.
Article 18(5): The Treaty Shield and Its Limits
Article 18(5) of the US-UK income tax treaty is the provision that rescues most Americans in British workplace schemes. Importantly, it survives the treaty's savings clause for US citizens, because the 2002 Protocol added paragraph 5 to the carve-out list in Article 1(5). Our guide to which treaty articles survive the savings clause walks through that list in full.
The Four Conditions You Must Meet
Article 18(5) applies only where you are a US citizen resident in the UK, you exercise employment in the UK, the income from that employment is taxable in the UK, and your pay is borne by a UK resident employer or a UK permanent establishment. Additionally, you must be a member of a pension scheme established in the UK, and the US competent authority must have agreed that the scheme generally corresponds to a US plan. In practice, the Exchange of Notes accompanying the treaty treats UK registered pension schemes as corresponding schemes, so the last condition is normally satisfied.
When those conditions hold, contributions you pay are deductible or excludable in the US, and contributions your employer makes are not treated as your taxable income. Therefore, for most British employees with a US passport, a salary sacrifice pension contribution is excluded from US income, at least up to the ceiling discussed below. Notably, the treaty adds that relief applies only to the extent the contributions qualify for tax relief in the UK, which matters when you breach the annual allowance.
The Ceiling Nobody on Payroll Mentions
Article 18(5)(b) caps the relief. Specifically, it cannot exceed what the United States would allow its own residents for contributions to a generally corresponding US pension scheme. For a defined contribution workplace scheme, the closest US equivalent is a 401(k) plan. According to IRS Notice 2025-67, the 2026 limits are $24,500 for elective deferrals under section 402(g), an $8,000 catch-up from age 50, a $11,250 enhanced catch-up for ages 60 to 63, and $72,000 for total annual additions under section 415(c).
The IRS summary of 401(k) contribution limits explains how those two ceilings interact in a domestic plan. Moreover, the compensation that a US plan may take into account is capped at $360,000 for 2026 under section 401(a)(17). That last figure rarely appears in expat guidance, yet it matters for any executive whose employer contributes a percentage of total pay.
Where the Treaty Stops Working Entirely
Several common structures fall outside Article 18(5) altogether. For example, if you are seconded to London but your salary is borne by a US parent company and merely recharged, the "borne by a UK employer" condition can fail. Similarly, the treaty does not cover the Channel Islands or the Isle of Man, so an international pension plan based in Jersey or Guernsey gets no Article 18 relief at all. Finally, if you move to Britain mid-year, only contributions attributable to your UK employment period qualify. In each case, the salary sacrifice pension contribution reverts to the default section 402(b) treatment and becomes taxable US income.
Elective Deferral or Employer Contribution? The Question That Sets Your Limit
This is the point where most US returns involving a salary sacrifice pension go wrong. Under UK law, a sacrificed amount is unambiguously an employer contribution. Under US law, however, an amount that you choose to receive either as cash or as a plan contribution is a classic elective deferral. That distinction decides whether your US ceiling is $24,500 or $72,000.
The Conservative Reading
On the conservative reading, a salary sacrifice pension contribution is economically identical to a 401(k) salary deferral. You elected to reduce pay in exchange for a contribution, which is precisely what section 402(g) regulates. Consequently, the generally corresponding US relief is capped at $24,500 in 2026, plus catch-up if you are 50 or over. Any excess becomes taxable US compensation in the year of contribution. Your employer's separate core contribution, which you never had the option to take as cash, sits alongside it under the $72,000 annual additions limit.
The Generous Reading
On the generous reading of a salary sacrifice pension, Article 18(5)(a)(ii) refers to "contributions made to the pension scheme by or on behalf of the individual's employer", and a UK sacrifice produces exactly that. Therefore, the whole amount is an employer contribution and only the $72,000 section 415(c) ceiling applies. This reading follows the treaty's own wording and UK characterisation. Nevertheless, it depends on the IRS accepting UK legal form over US economic substance, which is not guaranteed.
Our Approach in Practice
We model both readings for every client with a salary sacrifice pension. Where the two answers produce the same US tax, which is common for 45% taxpayers because of excess foreign tax credits, the choice matters less. Where they diverge, we document the position and disclose it on Form 8833. Our detailed guide to claiming a US-UK treaty position on Form 8833 explains when disclosure is required and what the IRS expects to see. Above all, the position must be consistent from year to year, because switching readings invites questions.
Catch-Up Contributions and US Plans You Already Hold
Article 18(5)(c) contains a rule that almost every guide overlooks. It says that contributions to a UK scheme which receive treaty relief are treated as contributions to a generally corresponding US plan when working out your eligibility for US plan benefits. Consequently, if you also defer salary into a US 401(k) in the same year, perhaps because you moved to London in June or because you draw a small US salary from a board role, the two plans share one elective deferral limit. A salary sacrifice pension in London and a 401(k) in New York cannot each claim a full $24,500.
The age-based catch-up works in your favour. If you are 50 or over, the conservative ceiling rises to $32,500, and between 60 and 63 it reaches $35,750. For a senior executive in that age band, the gap between the two readings narrows considerably, and the conservative reading often costs nothing at all. Therefore, check your age against the catch-up rules before assuming your salary sacrifice pension exceeds the US limit.
A Worked Case Study: A London Managing Director
The numbers below are illustrative, but they mirror the structure we see most often among senior employees of banks, asset managers and consultancies.
Claire's Position
Claire is a 46-year-old US citizen who has lived in London for nine years and works as a managing director for a UK asset manager with a well-established salary sacrifice pension scheme. Her contractual salary is £240,000. She sacrifices £40,000 into the firm's group personal pension, and her employer adds a core contribution of £12,000. Consequently, her P60 shows taxable pay of £200,000, and total employer contributions are £52,000. Her adjusted income for the UK taper is £252,000, which is below the £260,000 threshold, so her full £60,000 annual allowance applies.
In the UK, the salary sacrifice pension saves Claire £18,000 of income tax at 45% and £800 of employee National Insurance at 2%. Her employer saves £6,000 of secondary contributions. Her UK income tax on the remaining £200,000 comes to £76,203, because her personal allowance is fully withdrawn above £125,140.
The US Calculation Under Each Reading
Using an illustrative rate of $1.33 to the pound, her total employer contributions equal $69,160. On the generous reading, that sits below the $72,000 section 415(c) ceiling, so Article 18(5) excludes the lot. Her US wages are the $266,000 on her P60.
On the conservative reading, however, her £40,000 sacrifice equals $53,200 and is capped at the $24,500 elective deferral limit. Therefore, $28,700 becomes taxable US wages, lifting her US income to $294,700. After the 2026 single standard deduction of $16,100, her US tax before credits rises from about $56,424 to about $66,279, an increase of roughly $9,855.
Why She Still Pays No US Tax This Year
Claire's UK income tax converts to about $101,350. Because all her income is foreign-source general category income on Form 1116, her foreign tax credit wipes out her US liability under either reading. The real cost of the conservative reading is therefore not cash today. Instead, it is the $9,855 of excess credits that she can no longer carry forward, reducing her pool from about $44,926 to about $35,071 for the year.
That distinction matters later. Excess credits expire after ten years under section 904(c), and they are valuable if Claire acquires US-source income, receives a large taxable pension lump sum, or returns to America. Moreover, the $28,700 she paid US tax on becomes basis, or investment in the contract, which she can recover tax-free when she draws benefits. Without a year-by-year basis schedule, she would pay US tax on the same money twice.
Where Bonus Sacrifice Breaks Both Readings
Now suppose Claire also sacrifices a £40,000 bonus in the following year, hoping to use UK carry forward. With her usual £52,000 of contributions, total employer contributions reach £92,000, roughly $122,360. Even on the generous reading, that is $50,360 above the $72,000 ceiling. Furthermore, the UK taper now bites. Her adjusted income rises to £292,000, which cuts her annual allowance to £44,000, and her modest unused allowance from earlier years cannot cover the gap, so an annual allowance charge follows. Carry forward is a purely British concept in any case; the US limit resets every year and ignores unused UK allowance. Consequently, a large bonus sacrifice is where most American executives discover that their salary sacrifice pension is partly US-taxable.
FEIE, Foreign Tax Credits and the Excess Contribution
Whether the excess salary sacrifice pension contribution costs you real money depends heavily on how you file. Most high earners in Britain use the foreign tax credit, but some still claim the foreign earned income exclusion out of habit.
Why the Foreign Tax Credit Usually Wins
The UK's top rate of 45% exceeds the top US federal rate of 37%. Therefore, a UK higher or additional rate taxpayer normally generates excess credits that absorb any US tax on the portion of a salary sacrifice pension contribution above the treaty ceiling. The excess contribution is foreign-source earned income, so it falls in the same general category basket as your salary. As a result, the UK tax paid on your cash salary shelters the US tax on your excess pension contribution, even though HMRC charged no tax on the contribution itself.
When the Exclusion Makes Things Worse
The foreign earned income exclusion is $132,900 for 2026. Once you claim it, you cannot take a credit for UK tax on the excluded income, and revoking the election locks you out for five years without IRS consent. For a high earner, that usually means a larger US bill, because the exclusion covers only a fraction of pay while the credit pool shrinks. Moreover, IRS Publication 54 confirms that excluded income still counts when working out the rate on your remaining income. For most readers of this guide, the credit route is superior.
The Annual Allowance Charge Adds Another Layer
If your contributions exceed your UK annual allowance, HMRC claws back relief through the annual allowance charge. Importantly, Article 18(5) grants US relief only to the extent contributions qualify for UK tax relief, so the portion caught by the charge arguably loses treaty protection too. Our guide to the tapered annual allowance and its US tax cost covers the scheme pays trap in detail. Additionally, our UK pension annual allowance calculator models the taper, carry forward and the Article 18(5) ceiling side by side.
The April 2029 National Insurance Cap and What It Changes
The UK has already legislated the biggest change to salary sacrifice in a generation. According to the government's policy paper on salary sacrifice reform effective from 6 April 2029, only the first £2,000 a year of pension contributions made through sacrifice will remain exempt from National Insurance.
How the Cap Works
From 6 April 2029, any salary sacrifice pension contribution above £2,000 will attract both employee and employer National Insurance, exactly like ordinary employee contributions. Crucially, income tax relief is unaffected. The ICAEW's summary of the Budget measure highlights that the change targets higher earners and larger contributions. Meanwhile, the current National Insurance rates remain 8% for employees on earnings up to the upper earnings limit, 2% above it, and 15% for employers above the £5,000 secondary threshold.
What It Means for American High Earners
For a 45% taxpayer, the personal loss is modest, because employee National Insurance above the upper earnings limit is only 2%. The larger effect falls on employers, who lose up to 15% on every pound above £2,000. Consequently, we expect many firms to stop sharing their National Insurance saving and some to scale back sacrifice schemes entirely. In that event, you may switch to personal contributions with relief at source, which changes the US analysis because employee contributions fall under Article 18(5)(a)(i) as deductible contributions rather than excluded employer contributions.
What It Does Not Change
The cap does nothing to the US treatment of a salary sacrifice pension. The IRS ceiling remains the same whether or not HMRC charges National Insurance. Therefore, a salary sacrifice pension that exceeds the US limit today will still exceed it in 2029, and the elective deferral question remains exactly as open. If anything, 2029 is a sensible moment to restructure, because the UK advantage of sacrifice over personal contributions narrows sharply for anyone contributing well above £2,000.
Other Sacrifice Schemes, National Insurance and Social Security
A salary sacrifice pension is not the only benefit delivered through sacrifice, and the other schemes are far less friendly to US taxpayers.
Electric Cars and Cycle to Work
UK electric car salary sacrifice schemes are popular with senior staff because the benefit in kind rate for zero-emission cars is 4% for 2026/27. The US, however, gives no special treatment to company cars in general. Your reduced salary is replaced by a car benefit, and the IRS taxes the value of personal use under its own fringe benefit valuation rules. As a result, the US charge is typically far higher than the UK one, and there is little UK tax to credit against it. Similarly, a cycle to work scheme is exempt in Britain but has no US equivalent. Unlike a salary sacrifice pension, these schemes enjoy no treaty article at all.
National Insurance and Your State Pension Record
A salary sacrifice pension reduces your National Insurance, but for high earners it almost never threatens your State Pension record, because your post-sacrifice pay stays far above the lower earnings limit. Moreover, the US-UK totalisation agreement means a locally hired American pays into the UK system only, so sacrifice has no effect on US Social Security either. Nevertheless, if you are on a US secondment and pay US Social Security under a certificate of coverage, your UK sacrifice arrangement needs separate review.
Mortgages and Salary-Linked Benefits
As MoneyHelper's salary sacrifice guide notes, sacrifice can reduce the salary lenders use for affordability and can affect salary-linked benefits such as life cover. For US purposes, remember that a US mortgage lender will read your US return, which shows post-sacrifice wages and possibly an excess contribution add-back. Consequently, a clean, well-documented return helps when you buy property in America.
Reporting a Salary Sacrifice Pension on Your US Return
Getting the treaty position right is only half the job. The other half is reporting it consistently, disclosing it properly and keeping records that will survive an enquiry twenty years from now.
Wages, Form 8833 and Supporting Records
Start from the pay on your P60, which already reflects the sacrifice. Then add back any salary sacrifice pension contribution that exceeds your chosen US ceiling, translated at the rate for each contribution date. Attach Form 8833 disclosing the Article 18(5) position where required. Additionally, keep the sacrifice agreement, the scheme's registration details, annual member statements and a schedule separating sacrificed amounts from core employer contributions. Our US tax returns for expats service builds this schedule every year so that the basis you have already paid tax on is never lost.
Currency Translation and Monthly Monitoring
Because the US ceiling is fixed in dollars and your salary sacrifice pension is paid in pounds, the exchange rate alone can push you over the limit. A contribution of £54,000 is comfortably below $72,000 at $1.25 but exceeds it at $1.36. Accordingly, translate each monthly contribution at the rate for the date it was paid, or at the IRS yearly average rate if you apply that method consistently, and keep the workings. Moreover, if your employer pays a one-off contribution in March to use up the UK tax year, remember that the US measures the limit by calendar year. A single salary sacrifice pension contribution made on either side of 31 December can therefore land in the wrong US year and create an excess that a spread payment would have avoided.
FBAR and Form 8938
Your salary sacrifice pension is also a reporting item. A UK defined contribution pot is a specified foreign financial asset for FATCA reporting on Form 8938 once your thresholds are met, and many practitioners also include it on the FBAR filed with FinCEN. The FBAR position on workplace pensions is debated, but omitting a large pension from both forms is the most common failure we see. Our FBAR and FATCA reporting service resolves the valuation and disclosure questions for each scheme you hold.
Fixing Missed Years
Many Americans in Britain have excluded their salary sacrifice pension contributions for years without disclosing the treaty position, or have never filed US returns at all. If that describes you, the fix depends on whether you have filed. Where returns are missing, the IRS Streamlined Filing route normally brings you up to date with no failure-to-file penalties for non-wilful taxpayers. Where returns were filed but the treaty disclosure was omitted, amended returns and a protective Form 8833 are usually enough.
How TaxYork Can Help
TaxYork provides comprehensive US and UK tax return preparation for Americans on British payroll, and pension contributions are a core part of that work. We model your salary sacrifice pension under both the elective deferral and employer contribution readings, compute the excess contribution and its basis, test the annual allowance and taper, and prepare the Form 8833 disclosure. Furthermore, we coordinate your foreign tax credit pool across years, so that excess credits are preserved for the years when they matter most.
For clients with bonus sacrifice, carry forward or secondment arrangements, we review the salary sacrifice pension agreement, the scheme documents and the employment contract before the sacrifice election is signed. Additionally, our cross-border planning team prepares the return-side consequences of restructuring ahead of the April 2029 National Insurance cap. As a result, you know the US cost of each pound before it leaves your payslip.
Conclusion
A salary sacrifice pension is still one of the most valuable tools available to a high earner in Britain, and for most Americans Article 18(5) keeps it largely free of US tax. Nevertheless, the treaty caps relief at the level of a generally corresponding US plan, and the unresolved question of whether sacrifice is an elective deferral can move your ceiling from $72,000 down to $24,500. For 45% taxpayers, the foreign tax credit usually absorbs the difference, but it consumes credits you may need later and creates basis you must track.
Therefore, the sensible approach is to decide your reading, apply it consistently, disclose it on Form 8833, and keep a running schedule of contributions and basis. Moreover, review any bonus sacrifice before you elect it, and revisit the whole structure before the 2029 National Insurance cap arrives. Handled that way, your salary sacrifice pension delivers the UK savings it promises without an unwelcome surprise from the IRS.
Contact Us
If you sacrifice salary or bonus into a UK pension and hold a US passport, we can confirm your treaty position, calculate any excess contribution and prepare both returns. Please book a consultation with our US-UK specialists, email hello@taxyork.com, or call 020 3488 8606.
Disclaimer
This article provides general information about US and UK tax rules as they apply to pension contributions and does not constitute tax, legal or financial advice. Treaty positions depend on your individual facts, the terms of your scheme and your employment contract, and the law and published limits can change. You should obtain professional advice before acting on any point discussed here.