Cross-border tax & Global Mobility support for professional advisers.
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.
Specialist cross-border tax and global mobility support for advisers whose client matter requires international people-tax expertise alongside their own professional advice.
UK & overseas tax firms
Immigration lawyers
Employment lawyers
Reward consultants
Relocation companies
Recruitment firms
Audit firms
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Where specialist input adds to your advice.
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
When this needs immediate attention.
A client has asked a cross-border tax question outside the adviser’s core expertise
Answering without specialist input may create professional risk for the adviser.
Involving a specialist early protects both the adviser and the client.
A transaction, litigation, or employment matter has an international tax element
The adviser may deliver advice that is incomplete without the tax dimension.
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
UK residence, reporting, PAYE (UK employer withholding tax), and social security rules are jurisdiction-specific and frequently misunderstood from overseas.
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
The candidate or employer may face unexpected tax obligations, payroll costs, or social security exposure after the placement.
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
The client may act on immigration advice without understanding the tax cost or employer obligations that follow.
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
The audit finding may require specialist remediation advice covering payroll, reporting, social security, and treaty positions.
A specialist review can scope the exposure and recommend a remediation path.
Issue → Fenton support → typical output.
UK arrival/departure tax review
Written tax position covering residence, income sourcing, reporting, and employer obligation.
UK/US tax coordination
Coordinated UK/US analysis, treaty positions, and foreign tax credit review.
Cross-border equity and reward review
Jurisdictional taxing rights analysis and employer withholding position.
Tax and immigration coordination
Analysis of how the tax and payroll position interacts with the immigration timeline.
Employment tax input
Technical note on the tax treatment of termination, settlement, or restructuring across borders.
Technical defence and expert witness support
Written technical opinion, correspondence support, or expert witness report.
Pre-placement cross-border review
Analysis of employer obligations, payroll requirements, and social security position.
Specialist remediation scoping
Written assessment of exposure, remediation options, and recommended next steps.
UK specialist support for overseas firms
UK residence, payroll, social security, and reporting analysis.
Specialist second opinion
Independent technical review with written assessment.
What a proper answer needs to cover.
Cross-border matters often sit between professional disciplines. A complete answer needs to identify how each part interacts.
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
Professional adviser FAQs.
01 When should a professional adviser involve a cross-border tax specialist?
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.
02 Can Fenton work alongside my firm without taking over the client relationship?
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.
03 What tax issues should immigration lawyers consider when advising on a UK move?
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.
04 Can overseas tax advisers refer UK-specific matters to Fenton?
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, PAYE, payroll obligations, social security, reporting, and treaty positions. Fenton provides the UK-side analysis while the overseas adviser retains the overall client relationship.
05 Does Fenton provide expert witness support for disputes with an international tax element?
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.