We don't have settings about invoice reminder, right? It should be a feature request.
So, when the system send reminders and how can we change it?
Today the system sent invoice reminder 6 days before due date and I didn't find where it have this function. Where is this function?
At /modules/invoice/Services.php have the function getUnpaidInvoicesLateFor() that should send reminder 2 days after duedate. That is the "Executed action to send invoice payment reminders" at cron log.
I'll post soon my experience with FossBilling in production, using only the modules clients/service/invoice system with Asaas, a brazilian payment provider.