US Expat Tax Services for RSU Vesting Across Tax Years |
By US-UK Tax Advisors cross-border tax team · Last updated JUL 18, 2026
US Expat Tax Services for RSU Vesting Across Tax Years | US Expat Tax Services for RSU Vesting Across Tax Years US Expat Tax Services on RSU and Share...
Key Takeaways
- Covers a key US-UK cross-border tax topic
- Applies to US persons with UK ties and UK residents with US income
- Highlights the filing, reporting and tax-treaty points to check
- Get personalised advice before acting on your own facts
US Expat Tax Services for RSU Vesting Across Tax Years |
US Expat Tax Services for RSU Vesting Across Tax Years
US Expat Tax Services on RSU and Share Option Vesting
US expat tax services for Americans in the United Kingdom who hold restricted stock units or share options address a compensation structure that creates its own distinct sourcing and timing complexity — because equity awards are typically granted over a multi-year vesting period, and a UK-resident American who received the grant while working in a different country, or who moved between the US and UK during the vesting period, faces a specific allocation question about which country has the right to tax the vesting income. Furthermore, the value of vested RSUs or exercised share options is taxable as employment income in both the US and the UK — but the sourcing rules that determine how much of that income belongs to each country during a multi-year vesting period are governed by a specific day-count apportionment method that neither a UK-only nor a US-only tax adviser typically applies correctly without dedicated cross-border experience. Additionally, where the individual has moved between the US and the UK during the vesting period of a specific equity award, the sourcing analysis must trace the employment location for the entire vesting period from grant date to vesting date — not simply apply the current country of residence to the full value of the award. Consequently, the complete US expat tax services framework for RSU and share option vesting covers the day-count sourcing apportionment, the UK and US timing of the taxable event, the Form 1116 credit coordination across the sourced income, and the Schedule D treatment of any subsequent sale.
The Day-Count Sourcing Apportionment
How Multi-Year Vesting Income Is Sourced
Where a US citizen holds RSUs that vest over a multi-year period — typically three or four years from grant date — and works in different countries during that vesting period, the vesting income is sourced to each country based on the number of working days spent in that country during the vesting period, as a fraction of total working days across the entire vesting period. Furthermore, this day-count apportionment method is used by both HMRC and the IRS as the standard sourcing approach for multi-year equity compensation — meaning a consistent methodology can be applied to determine the UK-source and US-source portions of the same vesting income. Additionally, where the individual worked in the United States for the first eighteen months of a four-year vesting period and in the United Kingdom for the remaining thirty months, the sourcing apportionment allocates 37.5% of the vesting income to US workdays and 62.5% to UK workdays. Consequently, US expat tax services maintains a detailed workday log for every RSU grant with a multi-year vesting period — tracking the specific country of employment for each day of the vesting period from grant to vesting. The IRS equity compensation sourcing guidance is at https://www.irs.gov/individuals/international-taxpayers/foreign-earned-income-exclusion.
Grants Received Before the UK Move
Where an RSU grant was made while the individual was working in the United States — before any move to the United Kingdom — and vests after the individual has become UK tax resident, the UK-source portion of the vesting income is limited to the workdays spent in the UK during the vesting period, not the full value of the award at vesting. Furthermore, HMRC specifically recognises this apportionment for internationally mobile employees, meaning a UK-resident American does not pay UK tax on the entire vesting value merely because vesting occurs while UK resident. Additionally, the US-source portion of the same award remains fully taxable in the US regardless of the individual's current residence, since the US taxes its citizens on worldwide income regardless of source. Consequently, US expat tax services obtain the complete grant date, vesting schedule, and country-by-country workday history for every pre-move RSU grant — ensuring the UK self-assessment reflects only the UK-source apportioned amount rather than the full vesting value. The HMRC internationally mobile employee guidance is at https://www.gov.uk/hmrc-internal-manuals/employment-related-securities/ersm162000.
The Timing of the Taxable Event
RSU Vesting as the UK and US Taxable Point
For RSUs, both the UK and the US treat the vesting date — not the grant date — as the taxable event, with the fair market value of the shares at vesting taxed as employment income in both jurisdictions. Furthermore, this alignment between the UK and US taxable point simplifies the coordination compared to share options, where the taxable event can differ between the two jurisdictions depending on the option type. Additionally, the employer typically withholds UK PAYE tax on the vesting value through the payroll — selling a portion of the vested shares to cover the tax withholding — producing both employment income and a corresponding UK tax credit for the Form 1116 calculation. Consequently, US expat tax services confirm the vesting date fair market value and the UK PAYE tax withheld on that vesting event as the primary inputs for both the UK self-assessment and the Form 1116 general basket credit calculation. The IRS RSU guidance is at https://www.irs.gov/taxtopics/tc427.
Share Options and the Exercise Date Complexity
Unqualified share options are generally taxed at exercise in both the UK and the US, with the spread between the exercise price and the fair market value at exercise taxed as employment income. Furthermore, where the share option was granted under a UK tax-advantaged scheme such as Company Share Option Plan or Enterprise Management Incentive, the UK taxable point may be deferred to sale rather than exercise — creating a mismatch with the US taxable point at exercise that requires careful Form 1116 timing coordination. Additionally, where a UK tax-advantaged scheme produces a different UK taxable event date from the US taxable event date, the Form 1116 credit for the eventual UK tax must be matched to the correct US tax year based on the US taxable event, not the UK taxable event. Consequently, US expat tax services identify the specific UK scheme type for every share option grant — confirming whether the UK and US taxable events align or diverge before preparing the Form 1116 credit calculation.
Form 1116 Credit Coordination for Sourced Equity Income
Matching the UK Tax to the Correct Sourced Portion
Where an RSU vesting event has been apportioned between US-source and UK-source income under the day-count method, the UK PAYE tax withheld on the vesting relates to the full vesting value — not only the UK-source portion — because UK PAYE withholding does not itself distinguish between sourced portions. Furthermore, the Form 1116 general basket credit for this UK tax must be limited to the UK tax attributable to the UK-source portion of the income, since the general basket limitation calculation compares foreign-source income to the corresponding foreign tax. Additionally, claiming a credit for the full UK tax withheld against only the UK-source portion of income overstates the available credit and can trigger an IRS adjustment on examination. Consequently, US expat tax services apportion both the vested income and the UK tax withheld according to the same day-count workday fraction — ensuring the Form 1116 credit calculation uses consistent sourced amounts for both the income and the corresponding foreign tax. The IRS Form 1116 guidance is at https://www.irs.gov/forms-pubs/about-form-1116.
Schedule D Reporting for Subsequent Share Sales
The Vesting Date Basis for Future Capital Gains
Once RSUs vest and are taxed as employment income, the fair market value at vesting becomes the cost basis for any subsequent sale of the shares — with any further gain or loss between vesting and sale taxed as a capital gain or loss on Schedule D. Furthermore, the vesting date value must be converted to US dollars at the spot exchange rate on the vesting date to establish the dollar cost basis for Schedule D purposes. Additionally, where the shares are sold immediately at vesting to cover the tax withholding — a common arrangement called sell-to-cover — the small residual gain or loss between the vesting price and the actual sale price is typically minimal and easily calculated from the same-day transaction records. Consequently, US expat tax services record the vesting date dollar cost basis for every RSU tranche — using it as the Schedule D basis for the eventual sale, regardless of how many years later the sale occurs. The IRS Schedule D guidance is at https://www.irs.gov/forms-pubs/about-schedule-d-form-1040.
Case Study: RSU Vesting With a Mid-Vesting UK Move
Our team provides US expat tax services for a US citizen who received a four-year RSU grant from her US employer while working in San Francisco, then relocated to London eighteen months into the vesting period to lead the company's new UK office. Furthermore, the four-year grant vests in equal annual tranches, with the third and fourth tranches vesting entirely during her UK residence.
The US expat tax services sourcing analysis covered the following. Grant date: four-year vesting, 25% annually. Tranche one and two (years one and two): vested while working in San Francisco — 100% US-source, no UK apportionment required. Tranche three (year three): vesting period spanned six months in San Francisco and six months in London — sourced 50% US, 50% UK based on workday count. Tranche four (year four): vested entirely during UK residence — 100% UK-source, since the full twelve-month vesting period for this tranche fell within her London employment. Furthermore, for tranche three: vesting value $80,000. UK-source portion: $40,000 — reportable on UK self-assessment. US-source portion: $40,000 — not UK-taxable, fully US-taxable. UK PAYE was withheld on the assumption of full UK sourcing (a common employer payroll default) — requiring a UK self-assessment adjustment to reclaim tax on the US-source portion through the split-source claim. Additionally, Form 1116 credit for tranche three: only the UK tax attributable to the $40,000 UK-source portion is creditable — not the full PAYE withheld on the $80,000 vesting value. Consequently, the US expat tax services engagement corrected the employer's default full-UK-sourcing payroll treatment through a UK self-assessment split-source claim, apportioned tranche three between UK and US source using the day-count method, and calculated the Form 1116 credit using only the properly sourced UK tax amount.
Common RSU and Share Option Mistakes
Applying Full UK Sourcing to a Mid-Vesting Move
The most common RSU sourcing error is applying full UK tax to the entire vesting value simply because the vesting date occurs while the individual is UK resident — even where a significant portion of the vesting period was spent working in another country. Furthermore, UK payroll systems often default to taxing the full vesting value through PAYE without applying any workday apportionment. The correct approach requires US expat tax services to obtain the complete workday history for every multi-year vesting grant and file a split-source claim through the UK self-assessment where the payroll default has overtaxed the UK-source portion. HMRC guidance is at https://www.gov.uk/hmrc-internal-manuals/employment-related-securities/ersm162000.
Claiming the Full PAYE Tax as a Form 1116 Credit
Many advisers claim the entire UK PAYE tax withheld on a vesting event as a Form 1116 credit, even where only a portion of the vesting income is UK-sourced, overstating the available credit. Furthermore, this mismatch between sourced income and claimed credit can trigger an IRS examination adjustment. The correct approach requires US expat tax services to apportion the UK tax using the same workday fraction applied to the income, ensuring the credit and the income use consistent sourcing.
Not Tracking the Vesting Date Dollar Basis
Many RSU holders do not record the vesting date fair market value in dollars, making it difficult to establish the Schedule D cost basis accurately when the shares are eventually sold, sometimes years later. Furthermore, without this record, the cost basis may need to be reconstructed from historical share price and exchange rate data. The correct approach requires US expat tax services to record the vesting date dollar value for every tranche at the time of vesting — creating a permanent record for the future Schedule D calculation. IRS Schedule D guidance at https://www.irs.gov/forms-pubs/about-schedule-d-form-1040.
How US-UK Tax Can Help
At US-UK Tax, our team of Enrolled Agents, Chartered Tax Advisers, and Certified Public Accountants provides specialist US expat tax services for Americans in the UK who hold RSUs or share options. Furthermore, we maintain the complete workday history for every multi-year vesting grant, apply the day-count sourcing apportionment consistently to both income and UK tax withheld, file split-source claims through the UK self-assessment where payroll has over-withheld, confirm the UK scheme type for share options and identify any exercise-versus-sale timing mismatch, calculate the Form 1116 credit using properly sourced amounts, and record the vesting date dollar cost basis for future Schedule D reporting.
Contact our team today. Email hello@us-uktax.com call 0333-8807974, or visit https://www.us-uktax.com/contact/.
Conclusion
The US expat tax services framework for RSU and share option vesting rests on the day-count workday apportionment that determines the UK-source and US-source portions of any multi-year equity award — a methodology that both HMRC and the IRS recognise but that UK payroll systems frequently fail to apply correctly by default. Furthermore, the Form 1116 credit calculation must use the same sourced fraction for both the income and the corresponding UK tax — never claiming credit for tax withheld on income that was not actually UK-sourced. Moreover, recording the vesting date dollar cost basis at the time of vesting avoids the difficult reconstruction exercise that arises when shares are sold years later without a contemporaneous record. Contact US-UK Tax at hello@us-uktax.com or call 0333-8807974 today.
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FAQs
Q: How is RSU vesting income sourced between the US and UK?
A: By day-count apportionment — workdays in each country during vesting as a fraction of total workdays. Both HMRC and the IRS recognise this method.
Q: Does UK tax apply to the full RSU value if I moved to the UK mid-vesting?
A: No. Only the UK-source portion, apportioned by UK workdays during vesting, is UK-taxable. Payroll systems often incorrectly tax the full value by default.
Q: When are RSUs taxed — at grant or at vesting?
A: At vesting, in both countries. The fair market value at vesting is taxed as employment income and becomes the cost basis for any future capital gain.
Q: Can I claim the full UK tax withheld as a Form 1116 credit?
A: Only the UK-source portion. Claiming credit for tax on non-UK-sourced income overstates the credit and can trigger an IRS examination adjustment.
Q: Are UK tax-advantaged share options treated the same as RSUs?
A: Not always. Schemes like EMI or CSOP may defer UK tax to sale rather than exercise, creating a timing mismatch requiring careful Form 1116 coordination.
Q: What is the cost basis for shares sold after RSU vesting?
A: The fair market value at vesting, converted to dollars at the vesting date spot rate. Further gain or loss to the sale date is a separate Schedule D item.
