Equity is where cross-border tax gets expensive fastest.
Options granted in one country and exercised in the other. QSBS that the UK ignores; EIS relief the US ignores. An exit taxed by both. Founder equity rewards planning years before the liquidity event.
Your options don't travel well
ISOs lose their US magic if exercised while UK-resident; EMI options lose theirs to the IRS. Grant, vest and exercise can each be taxed by a different country depending on where you worked during the vesting period — apportionment the payroll systems rarely get right.
We map each grant against your residence timeline and plan exercise dates around the answer.
- ISO, NSO, RSU and EMI treatment across borders
- 83(b) elections and UK section 431 elections
- QSBS and EIS/SEIS — what survives a move
- Exercise and sale timing around residence changes
Plan the exit before the term sheet
By the time a sale is signed, most levers are gone. Residence in the year of exit, holding-period thresholds and the interaction of US capital gains with UK business asset disposal relief are all set in the years before. That is when to talk to us.
What we typically handle for you
- Grant-by-grant option review across residence changes
- 83(b) and section 431 elections
- ISO, NSO, RSU and EMI treatment both sides
- QSBS and EIS/SEIS preservation analysis
- Company structure: 5471, GILTI, check-the-box
- Exercise and sale timing around the move
- Exit year planning before the term sheet
- Both personal returns through the liquidity event
The services that usually apply
Questions we get about this
The gain is generally apportioned between the countries based on where you worked over the vesting period, rather than taxed wholly where you exercise.
That apportionment needs records of where you were, which is far easier to keep than to reconstruct.
It depends on the consideration, whether any of it is deferred or in shares, and where you are resident at completion.
The structure of the deal frequently matters more to your net position than the headline number does.
EMI and similar schemes are valuable under UK rules but the US does not mirror the relief, and the timing of taxation can differ sharply.
The scheme can still be worth joining - it just needs the US treatment understood before you rely on the UK figures.
Frequently by both, and rarely at the same moment. Grant, vest and exercise can each be the taxable event depending on the scheme and the country.
Where the vesting period spans a move, the gain usually has to be apportioned rather than assigned wholly to one side.
The US relief can still apply to qualifying stock, but HMRC does not mirror it, so a gain that is largely exempt in the US may be fully taxable in the UK.
That asymmetry is worth modelling well before an exit rather than at completion.
The UK reliefs can be valuable, but the US does not recognise them, and the underlying companies can raise PFIC questions.
The net position is frequently better than feared and occasionally much worse, which is exactly why it is worth checking first.
Last reviewed . Thresholds and rates change annually — check figures against the current tax year before relying on them.
Equity, a raise or an exit on the horizon?
The deal structure usually matters more than the headline number. Let us model it before you sign.