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Laurent Donnay de Casteau

Tax lawyer Brussels, Belgium

Laurent, tax lawyer at the Brussels Bar, is a partner and a tax specialist acting in all aspects of direct taxes (corporate and personal tax), both at international and Belgian levels. His extensive practice focuses on corporate structuring/restructuring, the tax aspects of M&A, private equity, investment funds, international mobility of employees and remuneration schemes, and high net worth individuals. He serves publicly-traded and closely held businesses, both at the level of the companies and the ultimate shareholders, in advising, tax audits, ruling requests and tax litigations.  He is also a member of the firm's French Desk.

He is a practical and efficient tax expert. Independent international legal directories (Chambers, Legal500, Leaders League) have acknowledged his reputation. Clients appreciate that he "is able to be innovative and can think outside the box to find answers" (Chambers, Europe, 2018). He is also described by clients as being "straight to the point, very smart and highly effective" (Chambers, Europe, 2019) and "a client-centric tax practitioner. He combines technical knowledge with clear explanations and valuable solutions" (Legal500, 2020). Leaders League ranks him for 2024 as "Excellent" in corporate tax and transfer pricing, and "Highly recommended" in wealth planning.

Laurent is adjunct professor at the prestigious business school ESCP-Europe (Paris) where he shares insights on international tax (focusing on international mobility, remuneration and stock options). His affiliations include the International Fiscal Association and the Brussels Bar. Before founding Advisius, Laurent served over 20 years in a top-tier Benelux law firm (Brussels and Paris offices) and an English law firm.

Laurent speaks French, Dutch, English and has good commands of Italian. 

Laurent’s academicals are law (UCL), economics (Leuven Management School – Vlerick), and tax (ESSF Brussels, and Harvard University -J.F. Kennedy School-).  

He is the author of several publications. Most recently he published articles and books about: 

  • 20 years of practice of the special tax regime on stock options; 
  • The new impatriates tax regime;
  • FR-BE cross-border real estate structuring;
  • Specific tax questions around the dissolution and liquidation of a company;
  • The new France-Belgium tax treaty: a detailed analysis from the Belgian perspective;
  • Taxation of artists in international situations;
  • The "substantial participation" clause in the new France-Belgium tax treaty from a Belgian perspective.


  • Louvain-La-Neuve (UCL), Law
  • Leuven (KUL/Vlerick), Economics
  • ESSF Brussels, Tax
  • Harvard University (J.F. Kennedy School), Comp. tax policy


  • French (native)
  • Dutch
  • English
  • Italian