Cross-border tax & Global Mobility support for professional advisers.
Professional Adviser Desk
Fenton International provides specialist cross-border tax and global mobility support to professional advisers where a client matter requires senior international people-tax input.
Fenton can work alongside existing advisers without displacing the client relationship.
Engagement is typically at Case Review level — senior judgement on a specific client situation where cross-border tax, employment tax, payroll, social security or reward expertise is needed alongside your own advice.
For more complex matters, Lead Counsel engagements allow Fenton to take the lead on the cross-border tax analysis and co-ordinate with your firm on the wider advisory picture.
How our Professional Adviser Desk provides this support.
→ UK & overseas tax firms
→ immigration lawyers
→ employment lawyers
→ reward consultants
→ relocation companies
→ recruitment firms
→ audit firms
→ A client matter has crossed into cross-border tax, payroll, or social security territory
→ Immigration, employment, relocation, or recruitment advice needs tax input to be complete
→ A UK or overseas tax position requires specialist international people-tax analysis
→ The adviser wants to retain the client relationship while bringing in specialist support
→ A dispute, litigation, transaction, or audit has an international people-tax dimension
→ The adviser needs a second opinion or technical review on a cross-border position
Examples of issues we support.
When this needs immediate attention:
A client has asked a cross-border tax question outside the adviser’s core expertise
→ What may be at stake: Answering without specialist input may create professional risk for the adviser.
→ Why early involvement matters: Involving a specialist early protects both the adviser and the client.
A transaction, litigation, or employment matter has an international tax element
→ What may be at stake: The adviser may deliver advice that is incomplete without the tax dimension.
→ Why early involvement matters: The international tax position can materially change the commercial outcome.
An overseas tax adviser needs UK-specific input for a client moving to or from the UK
→ What may be at stake: UK residence, reporting, PAYE (pay as you earn — UK employer withholding tax), and social security rules are jurisdiction-specific and frequently misunderstood from overseas.
→ Why early involvement matters: UK-specific advice prevents assumptions based on home-country rules.
A recruitment firm is placing an international candidate and the tax or payroll position is unclear
→ What may be at stake: The candidate or employer may face unexpected tax obligations, payroll costs, or social security exposure after the placement.
→ Why early involvement matters: A cross-border review before the placement starts can prevent problems for all parties.
Immigration advice has been given but the tax and payroll consequences have not been considered
→ What may be at stake: The client may act on immigration advice without understanding the tax cost or employer obligations that follow.
→ Why early involvement matters: Tax, payroll, and immigration timing often need to be coordinated before the move.
An audit has identified international people-tax exposure that the audit firm cannot resolve
→ What may be at stake: The audit finding may require specialist remediation advice covering payroll, reporting, social security, and treaty positions.
→ Why early involvement matters: A specialist review can scope the exposure and recommend a remediation path.
Issue → Fenton support → typical output
Client relocating to or from the UK that needs tax input
→ Relevant Fenton support: UK arrival/departure tax review
→ What you receive: Written tax position covering residence, income sourcing, reporting, and employer obligation
_____________
UK/US client where coordinated UK and US tax input is needed
→ Relevant Fenton support: UK/US tax coordination
→ What you receive: Coordinated UK/US analysis, treaty positions, and foreign tax credit review.
Client with equity, long-term incentives, or deferred compensation vesting internationally
→Relevant Fenton support: Cross-border equity and reward review
→What you receive: Jurisdictional taxing rights analysis and employer withholding position.
_____________
Immigration matter with tax, payroll, or social security consequences
→ Relevant Fenton support: Tax and immigration coordination
→ What you receive: Analysis of how the tax and payroll position interacts with the immigration timeline.
Employment law matter with cross-border tax dimensions
→ Relevant Fenton support: Employment tax input
→ What you receive: Technical note on the tax treatment of termination, settlement, or restructuring across borders.
_____________
Dispute, litigation, or HMRC enquiry with international tax element
→ Relevant Fenton support: Technical defence and expert witness support
→ What you receive: Written technical opinion, correspondence support, or expert witness report.
Recruitment firm placing an international candidate with unclear tax or payroll position
→ Relevant Fenton support: Pre-placement cross-border review
→ What you receive: Analysis of employer obligations, payroll requirements, and social security position.
_____________
Audit finding involving international people-tax exposure
→ Relevant Fenton support: Specialist remediation scoping
→ What you receive: Written assessment of exposure, remediation options, and recommended next steps.
Overseas tax adviser needs UK people-tax input
→ Relevant Fenton support: UK specialist support for overseas firms
→ What you receive: UK residence, payroll, social security, and reporting analysis.
_____________
Second opinion or technical review needed on a cross-border position
→ Relevant Fenton support: Specialist second opinion
→ What you receive: Independent technical review with written assessment.
What a proper answer needs to cover
Personal tax residence in each relevant country
Employer payroll, withholding, and reporting obligations
Social security and national insurance position
Immigration status and its interaction with tax timing
Employment law implications, including termination, contracts and jurisdiction
Equity, reward, and deferred compensation across borders
Treaty relief and foreign tax credit positions
Corporate tax and permanent establishment risk, where an individual's presence may create corporate tax exposure for the employer
Which adviser is responsible for which part of the answer
Whether the client has received advice from other firms that may conflict or leave gaps
FAQs
When should a professional adviser involve a cross-border tax specialist?
1
When a client matter involves personal tax, payroll, social security, or employer obligations arising from someone working, living, or earning across more than one country — and the adviser's own expertise does not cover the international people-tax dimension. Common triggers include relocation, international employment, equity vesting across borders, international recruitment, and cross-border disputes.
Can Fenton work alongside my firm without taking over the client relationship?
2
Yes. Fenton's model is designed to support existing advisers, not replace them. Fenton provides specialist cross-border tax and mobility input while the referring adviser retains the client relationship and primary advisory role. The scope, communication protocol, and client-facing arrangements are agreed in advance.
What tax issues should immigration lawyers consider when advising on a UK move?
3
Immigration and tax timing are closely connected. A client's UK tax residence start date, reporting obligations, payroll registration requirements, and social security position can all be affected by immigration decisions — including visa type, start date, and the sequence of entry. Tax advice should ideally be obtained before the immigration application is finalised.
Can overseas tax advisers refer UK-specific matters to Fenton?
4
Yes. Fenton supports overseas tax firms where a client is moving to, from, or through the UK and needs UK-specific people-tax analysis. This includes UK residence and domicile (the individual's long-term legal home for UK tax purposes), PAYE (pay as you earn — the UK employer withholding tax system), payroll obligations, social security, reporting, and treaty positions. Fenton provides the UK-side analysis while the overseas adviser retains the overall client relationship.
Does Fenton provide expert witness support for disputes with an international tax element?
5
Yes. Mark Abbs is a registered expert witness with the Academy of Experts. Fenton accepts instructions in cross-border tax disputes, HMRC enquiries, employment tribunal proceedings, and litigation where the international people-tax position is at issue.
Credentials and related insights
The Fenton Advisers Desk is led by Mark Abbs, a senior international tax adviser with more than 32 years’ experience, with 14 years as Tax Partner, Head of International and Senior Leadership Team member at a UK Top 8 firm. Over 16 years as a Senior Adviser in Big 4 firms (PwC, EY). He is a Fellow of the Association of Taxation Technicians, an IRS Enrolled Agent, and an accredited expert witness.
Our Advisory team has held multiple senior leadership and board-level positions in HR, reward, and governance, managing budgets, delivering and setting strategy, and boardroom scrutiny. We bring the practical judgement of people who have owned the problem — not only advised on it.