If you have a contract with a Customer where you bill the Customer on a
monthly, quarterly, half-yearly or annual basis, you can check the “Recurring
Invoice” box. Here you can fill in the details of how frequently you want to
bill this Invoice and the period for which the contract is valid.
ERPNext will automatically create new Invoices and mail it to the email ids
I’m currently on this feature now @Vipul_Patel, you can take a look in the first preview here https://youtu.be/t8eDZcDKVi8
The audio is in PT-BR, but I’m explaining, how to create a plan for an internet provider, that requires a Activation Fee, and a Hardware installation.