The modern workforce has expanded beyond the traditional fixed office work environment. Today, talent operates in a variety of work arrangements encompassing remote and hybrid working, as well as short-term international contracts. This shift has provided greater flexibility in how and where employees work, enabling businesses to access a global talent pool and streamline business operations across various geographical locations.

Global Mobility Tax encompasses the tax implications for both employees and employers when work occurs outside an employee’s primary tax jurisdiction. This framework governs how compensation is sourced, reported, and taxed across different countries. In today’s environment, where employees can work remotely from virtually anywhere, understanding these rules becomes critical for compliance and risk management.

Equity incentives are a form of non-cash compensation, including share options, restricted stock units (RSUs), and other stock-based compensation programs. Depending on where they were granted, vested, or exercised, these can create significant tax obligations that span multiple countries. This intersection of global mobility tax and equity incentives represents one of the most technically challenging areas of international tax, which requires careful planning.

This article explores the key components of Global Mobility Tax, how working across borders can impact your tax and strategies for managing potential tax liabilities.

With careful planning and expert guidance, individuals and businesses can leverage global mobility and equity incentives effectively while managing compliance risks. At DS Burge & Co, our team of expert advisors can help support your business in navigating these challenges through our specialised business tax services.

Table of Contents

The Impact of Remote Work

The rise of hybrid and cross-border remote work has introduced new tax complexities. Employees working remotely from different countries, even temporarily, may trigger unexpected tax exposures on their share-based pay.

Key considerations include:

  • Accidental tax presence: Employees working remotely from foreign countries may inadvertently create tax residency or permanent establishment exposures, particularly when working patterns extend over extended periods.
  • Hybrid work complications: Employees splitting time between multiple locations complicates tax allocation for both salary and equity compensation, requiring precise tracking of workdays in each jurisdiction.
  • Policy adaptation: The need for clear policies requiring advance approval and location tracking for all cross-border remote work.

These developments make it essential for businesses to maintain visibility over where employees are working, even in flexible arrangements.

Key Components of Global Mobility Tax

Income Tax Implications

When employees work across borders, their income tax obligations become significantly more complex. Most countries determine tax residency based on physical presence, typically using a Statutory Residency Test.

For employees participating in equity incentive plans, the situation becomes particularly complex. An employee might receive stock options in their home country, experience vesting while working in a second country, and exercise those options after moving to a third jurisdiction. Each of these events could trigger tax obligations in multiple jurisdictions, requiring careful tracking and allocation of taxable income between countries.

Social Security Considerations

Cross-border social security contributions represent another critical aspect of global mobility tax. Without proper planning, both employers and employees can face double contributions, requiring payments into social security systems in both home and host countries for benefits such as healthcare, pensions, and unemployment benefits.

The UK has established numerous reciprocal social security agreements designed to coordinate social security systems and prevent double contributions. These agreements include the UK-EU Trade and Cooperation Agreement, which coordinates systems to prevent double contributions. For UK employees working abroad temporarily, these agreements typically allow them to maintain their UK National Insurance contributions for a set period, often up to 24 months, by obtaining a certificate of coverage (such as an A1) from HMRC. This provides an exemption from social security payments in the host country in which they are working.

For equity incentives, the tax treatment of share-based payments for social security varies significantly by jurisdiction. Some countries treat certain awards as subject to contributions, while others do not. UK employers must understand each host country’s specific rules to ensure proper withholding and reporting in order to avoid potential penalties.

Payroll Tax Requirements

Managing global payroll becomes significantly more complex when managing employees in multiple jurisdictions. Businesses may need to operate payroll in multiple countries when employees exercise options or when shares vest, creating significant administrative burdens.

Equity withholding obligations present particular challenges, as companies must determine when and where to withhold taxes on equity transactions.

Double Taxation Treaties

Double Taxation Treaties (DTTs) play a crucial role in preventing the same income from being taxed in multiple jurisdictions. These DTTs typically include provisions determining which country has primary taxing rights over different types of income. For employment income, the standard approach grants taxing rights to the country where the work is performed, unless specific exceptions apply.

Global Mobility tax and equity incentives require careful planning and continual monitoring to ensure the correct amount of tax is paid. For more specific guidance on UK obligations, our team provides specialised support.

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Tax Equity Incentives

Equity-based incentives have become a fundamental component of an employee’s total reward package at various levels of seniority. Understanding how these incentives are taxed for employees operating in overseas locations is vital to ensure compliance and minimise the risk of double taxation.

Types of Equity Incentives

There are various forms of equity incentives rewarded to employees. The most common forms include:

  • Share Options: Grants employees the right to purchase company shares at a predetermined price. These can be ‘qualified’ options receiving favourable tax treatments or ‘non-qualified’ options taxed as ordinary income.
  • Restricted Stock Units (RSUs): Shares granted to employees after vesting conditions are met, typically continued service over a period. RSUs generally become taxable at vesting based on the fair market value of the underlying shares.
  • Stock Appreciation Rights (SARs): Rights to receive the appreciation in share value between the grant date and the exercise date, typically settled in cash or shares.
  • Employee Stock Purchase Plans (ESPPs): Shares programme allowing employees to purchase company shares, often at a discount to market price.

Each equity incentive carries its own distinct tax implications, particularly when participants work across borders during the life cycle of their awards.

Timing of Taxation

The timing of tax events for equity incentives varies significantly between jurisdictions, creating potential for mismatches that complicate cross-border tax compliance:

  • Grant Date: Generally not a taxable event for most equity awards, though some countries may impose reporting requirements at grant.
  • Vesting Date: The point at which restrictions lapse and employees gain full rights to their awards. For RSUs, this is typically the primary taxable event in many jurisdictions.
  • Exercise Date: For stock options, exercise typically triggers taxation on the spread between the exercise price and fair market value.
  • Sale Date: Disposition of shares acquired through equity awards may generate additional capital gains tax liabilities, particularly if the share value has increased since the taxable event.

These timing differences become particularly problematic when an employee changes countries between vesting and exercise dates, or when different countries characterise the same event differently for tax purposes.

Cross-Border Allocation Rules

When employees work in multiple countries during the life cycle of their equity awards, the question of how to allocate taxable income between jurisdictions becomes critical. Countries generally apply one of two approaches:

  • Time-based allocation: Taxing rights are allocated based on where the employee worked during the vesting period of the award. This method requires detailed tracking of work days in each jurisdiction. This is the UK approach
  • Residence-based allocation: The country where the employee is resident at the time of the taxable event (vesting, exercise) claims primary taxing rights.

The lack of international consistency in allocation approaches creates significant complexity for globally mobile employees and their employers. Without careful planning, employees may face taxation in multiple jurisdictions on the same equity income, while employers struggle with withholding and reporting obligations across different countries.

UK Tax Liability for Internationally Mobile Employees

Tax Treatment of Equity Awards in the UK

For internationally mobile employees, understanding the UK tax liability on equity incentives is crucial to avoid unexpected tax liabilities and compliance issues. Equity awards are taxed under two main categories:

  • Income Tax and National Insurance (NI): When shares vest or options are exercised, the gain is typically treated as employment income. This income is subject to both Income Tax and, for most employees, Class 1 National Insurance Contributions. For UK-based employees, this is usually collected in real-time through the PAYE system via payroll.

    If only part of the vesting (or option) period was spent working in the UK, the taxable amount for UK Income Tax and NI is generally apportioned based on the number of days worked in the UK during the relevant period compared to the total vesting period. This ensures that only the portion of the gain relating to UK duties is taxed in the UK.
    For NI, this may not always be the case if covered by reciprocal agreement.

  • Capital Gains Tax (CGT): When equity awards are sold, any increase in their value will be subject to Capital Gains Tax. The rate of CGT payable ranges from 18% for basic rate taxpayers to 24% for higher rate taxpayers, with an annual CGT allowance of £3,000. The disposal of equity awards must be disclosed to HMRC through a self-assessment.

    If shares are sold while you are non-resident for UK tax purposes, the gain is generally outside UK CGT. If sold while UK resident, the full gain is taxable in the UK, regardless of where the increase in value occurred.

UK Tax Return Filing Requirements

It can often be confusing for employees as to whether they are required to conduct a self-assessment tax return, particularly when leaving or entering the UK. The following scenarios are likely to result in the requirement of a self-assessment tax return:

  • You will likely need to file a UK Self Assessment tax return if you have received taxable equity income, even if it was processed through PAYE. This is often the case to reconcile any under- or overpayments and to report the gain officially.

If you leave the UK but part of your equity award’s vesting period relates to your time working in the UK, you will still have a UK tax liability on that portion of the award. In this scenario, you are required to file a UK Self Assessment tax return to declare this UK sourced income, as the PAYE system will not identify or deduct the correct tax. A tax return will therefore workout the correct tax.

Similarly, if you join the UK partway through an award’s lifecycle, you may have a UK tax liability on the portion of the award that vests after your arrival. This often requires filing a UK Self Assessment tax return, as income from equities is considered UK-sourced income and may not be fully captured by PAYE.

For guidance on completing a self-assessment tax return, minimising your tax obligations and ensuring your tax has been correctly calculated, speak to one of DS Burge & Co’s Chartered accountants.

Practical Examples: Arriving in and leaving the UK

Example: An Employee moving to the UK

Sara is granted shares as an RSU (Restricted Stock Unit) in the United States, her home country. Two years later, she relocates to the UK for work. Six months after arriving in the UK, a portion of her RSUs vests. Sara is required to pay the following tax:

  • Income Tax and National Insurance: The portion of the award that vests after she became a UK tax resident is subject to UK Income Tax and National Insurance. Her employer should operate PAYE on this income through the UK payroll. It is Sara’s responsibility to ensure that the correct amount of tax has been paid through PAYE.
  • Capital Gains Tax: If Sara later sells the shares while living in the UK, any gain from the value at vesting to the sale price is subject to UK Capital Gains Tax. This must be declared through a self-assessment tax return.
  • Filing Requirement: Sara will need to file a UK Self Assessment tax return to report any gains from a sale. It is also prudent for Sara to file a tax return to ensure the correct amount of tax has been collected through PAYE.

Example: An Employee leaving the UK

David, a UK resident, is granted share options. He has worked in the UK for two years of the four-year vesting period before relocating to Germany. He exercises all his options 2 years after leaving the UK.

  • Income Tax and National Insurance:A significant portion of the gain on exercise is taxable in the UK because it relates to the two years of work performed in the UK. The UK has taxing rights over this portion. David, even though a non-resident, will have PAYE deducted for his UK portion of the exercise period. This PAYE is often deducted incorrectly. A self-assessment tax return must be filed to disclose the income correctly to HMRC.
  • Capital Gains Tax: When David eventually sells the shares, the gain from the exercise price to the sale price is not subject to UK CGT if he is non-resident at the time of sale. He will be required to pay CGT in Germany, and this must be disclosed to the tax authorities.
  • Filing Requirement: David must file a UK self-assessment tax return to disclose the income earned from exercising the options. This scenario often surprises individuals who have left the UK, as they assume they are no longer required to pay UK tax.

Conclusion

In today’s interconnected business environment, managing global mobility requires careful attention to both standard salary and complex equity-based compensation. As we have explored, this involves navigating multiple tax jurisdictions, understanding varied social security requirements, and complying with different reporting obligations across borders. For internationally mobile employees, the UK tax liability on equity can be a particular minefield, with filing requirements often persisting after departure or commencing upon arrival.

Effective planning from both employee and employer is not merely beneficial but essential for maintaining compliance, preventing double taxation, and providing clear guidance to mobile employees. By implementing proactive strategies and maintaining accurate work location records, businesses can successfully manage these complexities while supporting their international workforce.

At DS Burge & Co, we specialise in helping businesses navigate global mobility tax implications through proactive tax and compliance planning. Speak to one of our specialist business tax advisors to ensure that your business is compliant and optimised for managing a mobile workforce.