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How Overseas Workday Relief actually gets calculated, and why it's harder than it looks

19 Jul 2026

If you've moved to the UK for work and heard about the FIG regime, you've probably also heard the number attached to it: up to four years of tax relief on income earned from days worked overseas. What's less discussed is how genuinely fiddly the calculation is, and why most people either overpay or underclaim without realizing it.

RSU sourcing runs on its own clock

Each RSU tranche is sourced over its own grant-to-vest window, not the date it happens to vest. That window can start well before you ever arrived in the UK, which means a tranche vesting today might be sourced across years you spent entirely overseas, entirely in the UK, or split across both. The overseas fraction for that specific tranche — worked out from workdays during its own grant-to-vest period — is what determines how much of it is exempt, and it will rarely match the fraction for your salary in the same tax year.

Bonuses are sourced by performance period, not payment date

Bonuses follow the same logic from a different angle: what matters is the period the bonus was earned for, not when it landed in your account. A bonus paid in March typically covers the prior year's performance period, so the workdays that count are the ones during that period — which, again, can predate your UK residence. Sourcing a bonus by its payment date instead of its performance period is one of the more common ways people get this wrong.

Currency isn't a single number

HMRC doesn't mandate one official rate for everything. Depending on context, yearly average, monthly average, or spot rates can all be valid, and payslip figures usually already reflect whatever rate your employer's payroll happened to use — not a single official number you can look up after the fact. That's why salary and other foreign income convert differently from RSUs and bonuses: for the former, an official average rate is the right choice; for the latter, the actual GBP figure on your payslip is the one that will reconcile with what HMRC and your employer already have on record.

Where FIG Tracker fits in

FIG Tracker's OWR calculator for RSUs and bonuses is a free tool built to handle exactly this: workday counting, per-tranche and per-bonus sourcing periods, and the right currency treatment for each income type, all kept straight automatically so the fractions line up with what HMRC actually asks for.

FIG Tracker is a calculation aid, not tax advice. Always verify your figures with a qualified tax advisor before filing with HMRC.

Frequently asked questions

Is there an OWR calculator for RSUs?
Yes — RSUs need their own calculator logic, not a simple day count, because each tranche is sourced over its own grant-to-vest period rather than the tax year it vests in. FIG Tracker sources every tranche individually and works out its overseas fraction from the workdays in that specific window.
Does OWR apply to a bonus paid after I've left the role or moved on?
What matters is the performance period the bonus was earned for, not when it's paid or whether you've since changed roles. A bonus paid after the fact is still sourced back to the workdays during the period it was earned.
What exchange rate should I use to calculate OWR on USD income?
It depends on the income type. Salary and other foreign income typically use an official HMRC average rate. RSUs and bonuses are usually best entered at the GBP figure your employer's payroll already used, since that's the number that will reconcile with your payslip and P60.