In order to change the default cost and billable rate, go to the ‘Settings’ section on the sidebar. In the ‘General Settings’ section, you can type new default cost and billable rates. Remember that default rates are on the bottom of “rates chain”, so you can always set different rates on the level of a certain member, project or user in a given project. Also, do not forget to save new settings after the configuration.
What is cost and billable rate
How to update the time entries billable and cost rates
How billable and cost rates are calculated per project and time entry