Recurring invoice
A recurring invoice is a template plus a schedule: the system issues the same invoice by itself at set intervals, monthly for example.
Updated:
Explanation
It saves work for subscriptions, monthly services and rents: nobody has to write the invoice by hand every month.
What matters is that only one invoice goes out per period, even if the system runs more than once.
How HelloTeam does it
In HelloTeam a recurring invoice's dates always follow the start date (an invoice on the 31st goes out on 28 February and on 31 March again), and the database allows only one invoice per period.
Module: Invoicing (€7.90 / month).