Services
Scope it, lock it, bill it.
Price the work, hold the scope, and see what each engagement earned.
Services priced like products.
Each service carries its own supplier costs next to its price, so a quote shows your margin before it goes out.
The scope is locked when the client accepts.
Any change afterwards is a new version, with the reason on the record and the one before it kept.
Time, invoices and what is overdue.
Timesheets, invoices and the money you are still owed sit next to what each engagement actually cost.