Is there a very simple billing? To know when the client should pay again?

Question

Billing systems

We provide website support services to a bunch of clients.
Payment periods are different for everyone: month / quarter / 0.5 years / year.
One client can have several services.
We need a relatively simple system that can:
1) Semaphore to the manager that these clients will soon have payment periods and need to issue invoices.
2) Automatically notify customers by email that they have a payment period.
3) So that customers can issue an invoice themselves or pay through some kind of robokassu thread or the like ..
Ie . we do not need any binding to the hosting, we do not need to block anything.

Answer 1

If it is still relevant, then, of course, there is an option for you: www.tixen.ru. The price will depend only on the number of customers. With the further development of the service no expenses required.