Billing rates for time entered in can be defined within a project, task, or user level. This can be configured within each client or project.
To do so, go to Settings > Company Settings > Clients & Projects. Then click next to the project or client you wish to configure > click on Edit. Select in the Default Billing Type drop-down, to calculate the billable rates based on the user’s default rate, the projects default rate, or the task’s default rate.
When a project is selected, the billable rate will now be calculated based on the default billable type.