The document details the best practices for automating the invoice approval process for PO and non-PO invoices, highlighting the challenges faced by companies, particularly with non-PO invoices. It distinguishes between PO invoices, which are associated with pre-approved purchase orders and have a faster approval process, and non-PO invoices, which lack such associations and generally have slower processing times. It emphasizes the importance of maintaining compliance and accuracy in invoice processing through defined workflows and automated systems like Aavenir's InvoiceFlow.