If previously scheduled invoices need to be rescheduled (e.g. sent on the 1st of the month instead of the 15th):
- Open the deal with the invoice(s).
- Go to the Billing Schedule tab.
- Click the recycle icon for the product(s) for which you want to change the invoicing.
- Click "Yes - delete unsent invoice(s)" to confirm that is your intention.
- Click the product again and set the new invoice schedule (custom / recurring, etc.)
- Click the "Save" button and you're done!