About Categories
Categories are a way of grouping items that share common characteristics. You can add, delete, and manage categories in the Labels pane of Billings Preferences. Slip categories are useful for grouping slips generally by the kind of work they are used to track. For instance, if you are a writer, you may wish to group slips in research, writing, and editing categories. In the Slip window, you can apply a category either to a new or existing slip by choosing one from the Category pop-up menu.
Billings comes with several predefined categories, but you can customize them to suit your working habits. Categories are also useful for reporting, including to find out how much time you spend doing certain kinds of work. They may also be useful if you want to send invoices that only list tasks that belong to a particular kind of work.