The Privacy Act 1988 (Cth) is the main Commonwealth law regulating how covered entities handle personal information. It is not limited to one narrow topic. The Act includes the Australian Privacy Principles, rules about tax file number information, a detailed credit reporting regime, privacy codes, notification of eligible data breaches, the functions and powers of the Information Commissioner, complaint and investigation processes, and enforcement mechanisms.
For a business owner, the practical point is that privacy law follows the full life cycle of information. It affects what you collect, why you collect it, what you tell people at the time of collection, how you use and disclose the information, how you secure it, whether it goes offshore, how you respond to access or correction requests, and what you do if something goes wrong. If your business uses online forms, customer accounts, booking systems, CRMs, payroll software, cloud storage, email marketing tools or analytics platforms, privacy issues are already part of your day-to-day operations.