Add a bookmark to get started

Guillermo Bailach

Legal Director

Guillermo Bailach is a tax lawyer with over 10 years’ experience advising multinational enterprises on M&A deals and designing bespoke tax-efficient international structures.

Guillermo is a Ph.D. in Law candidate at Complutense University of Madrid and his research focuses on international taxation. He completed his LL.M. at ie Law School and holds a Law Degree from Complutense University of Madrid.

Guillermo is a Professor of Tax Law at ISDE’s Law Degree and a Private Equity lecturer at ie Law School’s LL.M.

Guillermo is one of the most active members of the Firm in providing advice on the coverage of M&A transactions through W&I Insurance and leads the Tax Liability Insurance practice. He also has significant experience in advising on all types of tax procedures (tax audits and tax litigation) and provides day-to-day and M&A advice to a number of large multinational enterprises.


  • Advising leading underwriter of transactional insurance products on M&A deals for an aggregated value of more than EUR 8,000 million.
  • Advising on the tax structuring and financial modelling for the construction and development of a sugar factory in Spain with an estimated value of EUR 450 million.
  • Advising top transport company on tax aspects of a bidding process with an estimated value of EUR 430 million.
  • Advising several multinational enterprises in the Life Science sector of complex restructuring processes including a number of transnational mergers and de-mergers.
  • Spanish
  • English
  • PhD in Law (ongoing) at Universidad Complutense de Madrid
  • Master in Business Tax Advice (LL.M.) at ie Law School (Dean's List)
  • Law Degree at Universidad Complutense de Madrid


  • "El deber de secreto profesional de los abogados, ¿trinchera frente al ataque de DAC6?" - Cinco Días
  • “Ironías de la nueva Ley del Impuesto sobre Sociedades” - Expansión
  • “Discriminación impositiva a las inmobiliarias europeas” - Expansión
  • “El Suministro Inmediato de Información en el IVA: ¿cambio o revolución?” - Cinco Días
  • “Tregua a los productores españoles de obras audiovisuales extranjeras” - elEconomista


  • Professor at ISDE - Tax Law.
  • Coordinator at ISDE’s LL.M. – Tax procedures and taxpayer’s rights.
  • Lecturer at ie Law School - Tax regime of private equity.
  • Coordinator at UCM – Taxation on real estate transactions.

Prior Experience

  • 2013-14; Associate at big four
  • 2011-13; Trainee and Associate at Madrid based national law firm
Additional Information

Pro Bono Work

Guillermo also dedicates an important amount of time to pro bono matters for different NGOs, such as Fundación Infantil Ronald McDonald, Fundación Balia or Education for Employment.

Additional positions

Associated professor at ie Law School.

Memberships And Affiliations

  • Member of the Madrid BAR Association since 2012