Guglielmo Maisto founded Maisto e Associati in 1991. He is a professor of international tax law at the Catholic University. He acted as a consultant to the Ministry for European Community Affairs and as a member of the EU Joint Transfer Pricing Forum.

He is member of the delegated board of trustees of the International Bureau of Fiscal Documentation in Amsterdam, and represents the Italian Association of Industries at the OECD Business Industry Advisory Committee in Paris.

He is a member of several law societies, and of the editorial boards of various Italian and foreign tax legal journals. He is a member of the permanent scientific committee of the International Fiscal Association, and has acted as general and national reporter at several of its annual congresses.