Once you’ve customized what rates are available in your project, you can assign rates to team members.
If you assign one rate to a resource, all of their billable time for that project will be billed at that rate. If you assign a resource multiple rates, they will be able to choose which rate is used for the billable work they carry out in their timesheet.
To assign a billing rate:
A rates bubble displays.
Optionally, you can choose which rate is selected in the timesheet by default, by hovering over the rate, and clicking the Set as Default option that displays. Setting a default can help save time if one rate is used more often than the others.
Refer to Setting up a project for billing for information on this.