Xavier Rubert

Xavier founded Lullius in 2022 as an independent boutique focused on the most complex areas of Spanish tax law, private wealth and tax litigation.

Xavier has more than 15 years of experience. Before founding Lullius, he worked at leading firms including Cuatrecasas, Baker McKenzie and PwC. Throughout his career, he has advised major multinational groups, large technology companies, private equity firms, family-owned businesses and numerous high-net-worth and ultra-high-net-worth individuals on complex Spanish and cross-border tax matters.

His practice combines strategic tax advice with the defence of clients in high-stakes tax disputes. He is particularly experienced in matters where private wealth, business interests and multiple jurisdictions converge, providing senior-led advice from the earliest planning stage through to contentious proceedings.

Xavier has advised and defended clients at every stage of a tax dispute, before the Spanish Tax Administration, the economic-administrative tribunals, the High Courts of Justice, the National Court and the Supreme Court.

He holds a law degree from the University of the Balearic Islands and a Master's in Tax Advisory and Management (AGT) from ESADE in Barcelona. He has complemented his legal and tax training with executive programmes in Private Wealth Management at Chicago Booth and Global Taxation at IE Law School.

Xavier has been recognised in three consecutive editions of Best Lawyers: Ones to Watch in Spain (2023, 2024 and 2025) for his work in Tax Law. In 2026, he contributed to The Legal 500 Country Comparative Guides' Tax Disputes: Spain chapter and co-authored the Spain chapter of Chambers Global Practice Guides' Tax Controversy.

He speaks Catalan, Spanish and English.