Mariquita

Mariquita Barbieri, chair of Thompson Coburn’s Tax practice group, is a highly skilled tax and M&A attorney with a record of negotiating and closing complex, high-value transactions.

Drawing on her background as a former corporate counsel and trusted strategic advisor, Mariquita helps clients navigate sophisticated tax, operational, and strategic considerations while driving transactions to successful completion. She also serves as outside general counsel to businesses and investors, offering pragmatic legal, tax, and business guidance across industries.

A seasoned dealmaker, Mariquita has more than 20 years of experience leading and executing high-value mergers, acquisitions, divestitures, restructurings, and strategic transactions across a range of industry sectors, including technology, health care, financial services, manufacturing, energy, retail, food and beverage, real estate and construction, transportation and logistics, and entertainment and media. Having spent decades structuring and negotiating sophisticated transactions, managing due diligence, and navigating complex operational and regulatory challenges, Mariquita today focuses her practice on the tax structuring aspects of transactions and serving as tax counsel throughout the full lifecycle of a deal. Her transactional background provides the practical foundation to identify tax risks, develop efficient and creative structures, and guide clients through the business and tax considerations that arise from letter of intent through post-closing integration and operations. She works closely with business leaders, investors, lenders, and deal teams to optimize tax efficiencies, preserve value, and facilitate successful closings in highly competitive markets, while maintaining a practical, solutions-oriented approach focused on getting deals done.

With a Master of Laws in Taxation, Mariquita has a deep understanding of tax implications in corporate transactions. She handles private equity, hedge funds, joint ventures, and complex domestic and international tax matters, crafting innovative tax solutions for sophisticated business and investment structures. Her experience in tax-deferred reorganizations for multimillion-dollar corporations allows her to develop strategies that maximize value and minimize risk.

Mariquita also advises high-net-worth individuals, business owners, executives, family offices, and closely held companies on significant individual and corporate tax controversies and dispute resolution matters. Her practice includes negotiating with the Internal Revenue Service on audits, examinations, tax assessments, penalty abatements, refund claims, delinquent filings, voluntary disclosures, installment agreements, offers in compromise, and other IRS resolution programs. She regularly counsels clients on federal income tax compliance, tax risk mitigation, and strategic resolution of complex tax disputes, with successful outcomes ranging from favorable settlements and accepted offers in compromise to determinations of no further action by the IRS. Her experience navigating sensitive tax matters involving business operations, ownership transitions, and cross-border issues allows her to deliver practical, results-oriented strategies while minimizing financial and reputational exposure.

With in-house counsel experience at a Fortune 500 bioproducts company, Mariquita offers a unique perspective on regulatory compliance, particularly with FDA, USDA, EPA, and IRS-related compliance and reporting matters. She has led initiatives to create best-practice compliance frameworks, manage internal ethics investigations, develop crisis management strategies, and implement operational protocols designed to reduce corporate risk and exposure. While in-house, Mariquita also served as the U.S. data privacy lead, advising on the implementation of global privacy and data security programs, including GDPR compliance, and she continues to help clients navigate the complexities of data protection. Her experience working across highly regulated industries and advising on complex compliance environments further strengthens her ability to navigate sensitive tax controversies, IRS examinations, regulatory inquiries, and tax risk management matters while helping clients develop practical governance and compliance best practices. Adept at aligning cross-functional teams and navigating evolving regulatory landscapes, Mariquita facilitates seamless transitions and operational synergies throughout a company’s life cycle and after a strategic transaction.

As corporate counsel and assistant secretary at a division of DuPont Nutrition & Health, Mariquita served as general counsel for three major divisions, managing corporate matters, trade compliance, employment law, tax planning, tax controversy matters, and M&A transactions. Her collaboration with business leaders protected intellectual property, secured trade secrets, and facilitated licensing, strategic transactions, and cross-border sales throughout North America, Europe, Asia-Pacific, and Latin America. Working closely with finance, accounting, and operational leadership teams, she advised on transaction structuring, tax-efficient business operations, compliance processes, and enterprise risk management initiatives designed to support long-term growth and operational efficiency. With a track record in identifying and closing strategic deals, optimizing transaction structures, and navigating complex regulatory and tax considerations, Mariquita has driven significant business growth, expanded capabilities, and delivered shareholder value.