If you are charging your clients a flat fee in addition to the hourly billing, you might want to add that flat fee (with a description as to what the fee is for) to the hourly invoice. In Core, this can be done in the following way:
- Open the Projects screen and create a separate project (or create it as a phase of the existing hourly project).
- Set the project's Contract Type as Fixed Fee. Check Create Projects from Scratch or Add Project Phases for details, depending on your preference.
- In the detail view, enter the project description in the Memo field.
- Next, go to its Rules & Contacts tab and add the rule 'Show memo on invoices'. Save all the project information. Check Assign Rules to Projects for details.
- Finally, open the Invoices screen and create a joint invoice for the hourly and fixed fee projects so that they end up on the same invoice. Check Combine Invoices for details.