The most beneficial stage of the system development life cycle (SDLC) to consider data privacy principles is D: Requirements definition. This is because data privacy principles should be integrated into the design and development of customer-facing IT applications from the very beginning, not as an afterthought or a retrofit1. By considering data privacy principles in the requirements definition stage, the developers can identify the personal data that will be collected, processed, stored, and shared by the application, and ensure that they comply with the relevant laws and regulations, such as the General Data Protection Regulation (GDPR)2. They can also apply the principles of data minimization, purpose limitation, transparency, consent, and security to protect the privacy rights and interests of the customers3.