I have published my first WHMCS web host billing system addon and it has been listed with WHMCS at https://www.whmcs.com/appstore/2458/InvoiceDate-2-DueDate.html
Here are some details:
This WHMCS addon module changes the invoice date to be the same date as the due date for automatically generated invoices by cron and invoices initiated from the admin area for individual clients created by selecting “Generate Due Invoices”.
Changes are made before any automatic e-mails are sent out.
Use this if you would like to set your invoice dates to be the same as your service renewal (due) dates but you still want to send advance notices to your users.
- Changes auto-created invoices’ due date from the generated date to the due date
- Use it when switching from ClientExec which only has the due date and you want to keep it similar for your users