Sharesave, SIPs and EMI options when you also answer to the IRS

It is one of four schemes that HMRC approves: Share Incentive Plans, Save As You Earn, Company Share Option Plans and Enterprise Management Incentives. Within their conditions, you pay no Income Tax or National Insurance on the benefit.

Each works differently. Some give shares, some give options, and some combine savings with an option at a fixed price.

The GOV.UK guide to employee share schemes lists the four and their conditions. Shares offered outside them carry ordinary employment tax instead.

Because approval is a British concept that exists only in British law. The US has its own favoured plans, with their own statutory rules, and a UK scheme does not meet them simply by satisfying HMRC.

So for an American employee, a Sharesave or EMI option is generally just an option. The special British treatment stays in Britain.

This mirrors how the US treats ISAs and other UK wrappers. Our guide to US compliant investing from the UK covers the wider pattern.

Usually as an ordinary option, taxed when you exercise. The GOV.UK Sharesave guide explains the British side of the same option. The IRS explains that for such options you include the value of the shares at exercise, minus what you paid, in income. That spread counts as ordinary income in the year you buy the shares.

Growth after exercise then becomes a capital gain or loss when you sell. The IRS page on stock options sets out the general rules.

The savings contract itself raises a smaller point. Any bonus on the savings is interest-like income for American purposes, even where Britain leaves it untaxed.

Much the same as Sharesave on the American side. The US generally treats them as options without special status, so the spread at exercise is taxable income for a US citizen.

In Britain, exercising within the scheme rules usually brings no Income Tax. Capital gains tax then applies when you sell, measured from what you paid.

EMI options often sit in fast-growing private companies. The spread at exercise can therefore be large, and the shares may not be easy to sell to fund the American tax.

A SIP can give free shares, matching shares, partnership shares bought from salary, and dividend shares. The British reliefs depend on how long the shares stay in the plan trust.

The American rules look at when you receive the benefit, not at the trust period that drives British relief. The GOV.UK SIP guide explains the holding periods on the British side.

Partnership shares show the mismatch clearly. Britain lets you buy them from salary before Income Tax, while the US still taxes that salary as wages.

It sits in the gap between the two taxable moments. The US taxes the spread as income at exercise, while Britain charges nothing then and taxes the whole gain from your purchase price when you sell.

So the same slice of value, the spread at exercise, can attract American income tax in one year and British capital gains tax in another. The two charges differ in type and in timing.

Credits are the usual answer to double tax, but they work best when both countries tax the same income at the same time. Whether relief bridges this gap depends on the treaty and the facts, so it is not automatic.

Because the British scheme worked exactly as designed. With no Income Tax at exercise, the American return has no British tax on that income to credit against the US charge. That surprises people who assumed approval would protect them everywhere.

Excess credits can still help. The spread is pay for work done in Britain, so surplus British tax on your salary may absorb some or all of the American charge. Whether it does depends on how much surplus you have.

Our guide to avoiding double taxation explains how credit categories and carryovers work.

Then the mismatch runs the other way round. US parent companies often offer an employee stock purchase plan with favourable American treatment, and Britain does not recognise that status at all.

For a US citizen, a qualifying American plan can defer US tax until sale. Britain may instead charge Income Tax on the discount when you buy the shares.

The result is British tax early and American tax late, the mirror image of Sharesave. Some US companies offer a separate UK version to avoid exactly this, so check which plan you actually joined.

Timing is the main lever, and it is usually within your control. Exercising and selling in the same tax year brings the American and British charges closer together, which can make relief easier to line up.

Using the British annual exemption for capital gains, spreading sales across tax years, and choosing when to exercise all change the combined bill. None of them removes the mismatch completely.

In our practice we see the biggest savings come from modelling before exercise rather than after. Once the shares are bought, the American income is already fixed.

Within an approved scheme, Britain charges no National Insurance on the benefit. The American side is less predictable, because payroll tax follows its own rules on wages and the social security agreement.

Where the agreement places you in the British system, US Social Security tax does not normally apply to your earnings. Our guide to National Insurance for Americans explains which system covers you.

Check how your employer reports any US-taxable amount. A British employer will not usually issue an American wage form for a Sharesave exercise.

The scheme rules decide what happens to the option, and leaving often shortens or ends it. Good leavers, such as those made redundant, may keep a right to exercise for a limited time.

Exercising early under leaver rules can bring British Income Tax that the scheme would otherwise have removed. So the British advantage may shrink at exactly the moment the American charge arrives.

If you plan to move back to the United States, check the leaver provisions first. The date you resign can change what both countries charge.

Both returns report the sale, each from its own starting cost. The American cost includes the spread you already paid income tax on, while the British cost is usually what you paid.

That difference means the British gain is larger than the American one on the same sale. Keep the exercise statement, which shows the market value and the price paid.

Our guide to capital gains tax on shares covers the British calculation, including how shares acquired at different times pool together.

It can, because options are earned over time rather than on a single day. Where you worked in both countries between grant and vesting, each country may tax the part linked to work there.

HMRC splits that income by workdays across the earning period. The American side taxes a citizen on the whole spread and relieves the overlap through credits.

Keep a record of where you worked while each option was earned. Without it, neither return can support the split.

Work through this list before exercising any option under employee share schemes. It takes an afternoon and can change the combined bill noticeably.

Keep the results with the scheme documents, since both returns will need them.

Take an illustrative example: an American in Bristol joins her employer's Sharesave and, three years later, exercises options well below the market price. She holds the shares for another year and then sells.

In Britain, the exercise costs nothing, and she pays capital gains tax on the sale above her option price. On her US return, the spread at exercise is income in the year she bought, with no British tax that year to credit.

Had she sold within the same tax year as exercising, the two charges would have sat closer together. The total would still exceed a British colleague's bill, but by less.

The first is assuming HMRC approval travels. It does not, and the US taxes the benefit on its own timetable.

The second is exercising a large option without modelling the American tax. The cash for that tax often has to come from somewhere other than the shares.

The third is using the wrong base cost on each return. The American and British costs differ, and mixing them up misstates both gains.

The fourth is forgetting the savings bonus and dividend shares. They are small, but they still belong on the American return.

We model exercises and sales across both returns through our treaty relief service, including how relief lines up across the two charges. Where a better sequence exists, we show it before you act.

If you hold options under employee share schemes, send us your plan statements and we will map the American position at a fixed fee agreed first. This article is general information, not personal tax advice; take advice on your own facts from a qualified adviser.