Thierry Irrthum's main area of practice is individual taxation, both nationally and internationally. In particular, he assists individuals in their tax dealings with the Swiss authorities, including tax returns, asset restructuring, real estate transactions, negotiation of pre-contracts and inheritance matters. His practice also extends to voluntary disclosure procedure.

Thierry Irrthum studied at the University of Geneva, where he obtained a Master of Science in Business Management (2005). Before joining Walder Wyss, he practised tax law with a major international consulting and tax services company and then with another major Swiss law firm specialising in tax matters.

Thierry works mainly in French and English.