Within Preferences you can add your billing rate and unit:
- Billing rate: This is your standard rate for the time billed against your clients, this figure will always use the currency pre-selected in your company settings. Click on the field to enter the rate.
- Billing unit: This is set to hours by default.

If you need to change your billing rate for a one-off project or client, you can do this as and when needed when creating or editing your time item within the app itself.