Mayer Brown has a sophisticated tax controversy practice representing clients in high-stakes disputes, including transfer pricing adjustments, partnership taxation controversies, and economic substance challenges. The team regularly handles IRS examinations, administrative appeals, and litigation in federal courts. The practice is jointly led by New York-based Brian Kittle, who advises on transfer pricing disputes, business purpose doctrine matters, and complex partnership controversies, and Chicago-based Thomas Kittle-Kamp, whose work centers on litigation arising from partnership and corporate transactions, including economic substance and transactional recharacterization issues. Also in Chicago, John Hildy represents clients in high-value federal tax disputes and transfer pricing cases. Leah Robinson focuses on capital gains tax litigation, while Joel Williamson advises on leveraged partnership transactions, transfer pricing disputes, and proceedings before the IRS Office of Appeals. Rachel Borden joined from the IRS in August 2025 and concentrates on examinations, administrative appeals, and technical controversy matters.
Legal 500 Editorial commentary
Testimonials
Collated independently by Legal 500 research team.
- ‘Jason Osborn is an invaluable advisor. His strategic thinking, advocacy skills, and communication and relationship management abilities are all top notch. Tom Kittle-Kamp’s breadth and depth of IRS experience make him a strong asset to any controversy team.’
- ‘Very practical and easy to work with. Mayer Brown is generally more resolution oriented than many leading controversy firms and often seeks strategies to de-escalate and resolve complex issues rather than default to litigation.’
- ‘The Mayer Brown tax controversy team brings exceptional strategic vision and pragmatism to its matters. They identify the right path forward, and their billing is consistent with the value delivered.’
- ‘Brian Kittle is responsive and communicates clearly. He identifies solutions that others may miss and brings the interpersonal skills that are critical in tax controversy matters.’
Key clients
- Abbott Labs
- American Express
- American Axle & Manufacturing
- Aon plc
- Avient Corporation
- Canadian Imperial Bank of Commerce (CIBC)
- Eaton Corporation
- FMR LLC (Fidelity)
- General Mills
- GSS Holdings (Liberty Street)
- John Laing
- Keysight Technologies
- Occidental Petroleum Corporation
- Tribune Media Company (Nexstar Media)
- Visa Inc
- Stripe, Inc.
- Sun Pharma
- Yum! Brands, Inc.
Work highlights
Representing Avient Corporation in its U.S. Tax Court case involving the question of whether a capital loss may be recognized following an intercompany sale of stock under IRC section 304.
Representing Visa, Inc. in the US Court of Federal Claims to secure a $520 million refund.
Representing Keysight Technologies in the first case filed challenging the validity of the GILTI regulations in the Court of Federal Claims.
Lawyers
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Leading partners
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Practice head
Brian Kittle; Thomas Kittle-Kamp
Other key lawyers
Jason Osborn; Joel Williamson; Leah Robinson; John Hildy; Rachel Borden