Whether you always charge by the hour for your services or use this infrequently, defining your charging rates is a useful way to save time by being able to select from a preset selection.
Select the 'Settings' icon in the left-hand menu bar and select 'Billing'.
From here, you can see that you have a default rate which can have a description and cost per hour.
By selecting the + sign to the right of this rate will allow you to add a further rate. For example, Standard Rate, Out of Hours, Discounted etc.
Setting Chargeable Time Increments
Your business may charge by the hour or part hour; in which case, you can set up the increments by which your field workers time is charged.
In the same screen, (Select the 'Settings' icon in the left-hand menu bar and select 'Billing'), under the Payment Terms you can adjust the time increments in which you wish to bill (in minutes):
Don't forget to select 'Save' before you move away from the page.