There are many ways to handle the invoice process. There are many billing softwares out there. Some of the are free and with limited functions and others cost a lot of money but have all the tools you need to run a small business integrated.
When employment starts, so does the employer_employee relationship. This type of relationship is defined by the kind of contract the employee has in the company. It revolves around the things they talk about and disclose to each other before the start of the employment. And before such employment, it is necessary that the company has certain basic information about the employee. This is basically for accountability purposes and for the sake of having a complete and uniform record of all employees.