Matheson


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Mark O'Sullivan

Partner

Palo Alto

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Mark O'Sullivan is praised for his "impressive technical ability".

Who’s Who Legal 100

Expertise

Mark O’Sullivan is a partner in the firm’s Tax Department and advises on all aspects of Irish corporate taxation. His primary focus is advising overseas clients establishing operations and doing business in and through Ireland. Mark also advises extensively on all aspects of international tax planning, including IP planning, cross-border reorganizations and financing transactions.

Mark was previously seconded to the legal department of a large investment bank in London in 2004. Mark has been based in the firm's Palo Alto office since 2007.

Mark is an active member of the Tax Section of the American Bar Association (ABA), the International Fiscal Association and is also a member of the New York City Bar Committee on Taxation of Business Entities. Mark regularly speaks on international tax issues at Tax Section meetings of the ABA and has presented at a number of Tax Executives Institute (TEI) seminars. Mark has also published articles in the International Tax Review,  the Irish Taxation Review, IFLR, BNA and Finance Magazine.

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Accolades

Interviewees appreciate Mark O’Sullivan’s "help with strategy and regulatory issues. It has been really superb.
Chambers Europe 2016

Tax expert
Euromoney Expert Guide 2015

Mark O’Sullivan is widely acclaimed for his strength in advising overseas clients on international tax planning and cross-border reorganisation cases involving Irish tax issues.
Chambers Global & Europe 2015

Mark O’Sullivan specialises in all aspects of Irish corporate taxation and received praise for his "impressive technical ability".
Who’s Who Legal 100 2014: Corporate Tax expert

Based in the firm's Palo Alto office, Mark O'Sullivan is notably experienced in advising US companies on Irish tax issues. He recently advised Eaton on the tax aspects of its acquisition of Cooper Industries.
Chambers Global 2014

The well-regarded Mark O'Sullivan operates from the firm's Palo Alto office and advises US companies on foreign direct investment projects into Ireland.
Chambers Global 2013

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Education

Qualified as a solicitor in Ireland
AITI / Chartered Tax Adviser (CTA)
University College Dublin (Diploma in Financial Services Law)
University College Dublin and Université de Toulouse (BCL)

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