Allow upgrading / downgrading after invoice generation
Since WHMCS does not send out a pre-invoice notice, customers may decide to upgrade or downgrade their plan after they receive an invoice for service. This is more common with annual or longer payment terms. It is a common request for customers to want to downgrade or change from triennial to annual at their renewal but usually after the invoice is generated.
Please add the ability for customers to downgrade or upgrade or change billing terms even after the invoice is generated (I have created a mod to handle billing cycle changes, I know it isn't difficult to do).
This should be as simple as cancelling the current invoice, changing terms and calculating the new payment, invoicing the customer and implementing the change once the invoice is paid. As an example, I do not issue credits on downgrade, so it does not work for a customer to pay the invoice and then downgrade and receive a credit. That would end up with another manual step of issuing a payment gateway refund for the overpayment too. Let's simplify things and not limit our customers on what they can do with their accounts.
Simple request: Please allow customers to upgrade / downgrade and change billing cycle even after invoice generation by updating or reissuing invoice for new payment terms.
Even if you just give us as admins the ability to reissue or generate a new invoice after cancelling the old and making service changes.