In the practical sub-module on principles of personal data processing, examples of personal data processing during which one or more principles of personal data processing were violated are described. The aim of this practical module is to make it easier for entrepreneurs to understand the principles from Article 5 of the General Data Protection Regulation through concrete examples from practice. After reading the description of the situation in which there was a violation of the principles of personal data processing, it is necessary to determine the violation of which principle (one or more of them).