Set an account default hourly rate in Invoicing settings, or a default rate on a Contact. New time entries use the project rate first, then the linked Contact rate, then the account rate. A rate entered directly on an entry takes precedence. Contact and account defaults use the context default invoice currency. Each new entry keeps its own rate and currency, so changing a default does not change saved time.
Hourly rate defaults for Time Tracking
Set account and Contact hourly rates that fill new time entries when a project has no rate.