I've been saving the invoices before I send them out. After I send it to the customer, the invoice is still listed on the dashboard under "Ready For Invoice", even though I've had confirmation that it's been sent. Should I delete them?
Yes you should be good to delete those if the invoice has been sent and there is still a draft. If the order is still open you can also close the workflow on the order by pulling up the PO and there are a few icons on the top right of the form and one of them will allow you to close that order.