There are various legal grounds for processing of personal data. Consent is one basis. Another basis is the balancing of interests. Extra care must be taken when balancing interests when it comes to personal data concerning children. A third basis is agreements. A fourth basis is a legal obligation to process data (where companies e.g. are required to register information in order to fulfill obligations imposed by law). Note that personal data may only be collected for explicit and justified purposes and not later processed in a way that is incompatible with them. As an example, it can be mentioned that data in payroll systems are generally processed based on agreements and legal obligations, data in customer registers are processed based on agreements (for certain information, consent is also required) and data on websites are generally processed based on consent or balancing of interests.