Source: OECD (2020), Tax Administration 3.0: The Digital Transformation of Tax Administration, OECD, Paris. http://www.oecd.org/tax/forum-on-tax-administration/publications-and-products/tax-administration-3-0-the-digital-transformation-of-tax-administration.htm Building block 1. Identify, authenticate and autorize individuals and companies (or company representatives) Stages: password based, ID card, Mobile app, Facial / fingerprint, multifactor (based on the level of security required)