A monthly invoice does not have to be retyped
A recurring template holds the client, the lines, and the interval. You generate the next invoice from it.
The template is not the invoice
Save a retainer or a monthly order as a recurring template. Weekly, monthly, or yearly. The template remembers who to bill and what the lines are.
You generate the next one
When the date arrives, generate the invoice. It gets its own number. The next date moves forward: seven days, thirty days, or a year. Wire Invoice does not send it by itself, and it does not collect the wire.
Change the template, not the old invoice
If the fee changes, edit the template. Invoices you already sent stay as they were.