New billing logic
I think,WHMCS need change it's order,renew and invoicing logic.
We have over 10000active user and 20000services, we have many unpaid invoice every day,and it make our whmcs dirty.
I've suggest new order/renew logic to made it better.
On order,We do not need invoice before customer payment.I think it's better we have quote at end of order process and if the customer make payment,The quote automatically change to invoice. also we need an producer to auto cancel quotes.
On renew,We do not need invoice! We need a page to show list of near expiring services to customer. Customer should select services who want and then, make an quote for the services and if the quote paid,services should be renewed.