Large companies, with established procurement processes, require a structure to manage POs and match them to invoices. Equinix Metal should support customers creating and updating a list of Purchase Orders and some basic rules to assign them to invoices (e.g. by Project) or support manually matching and update an invoice with a PO entry. A good example of this can be found at AWS here: https://aws.amazon.com/aws-cost-management/aws-purchase-order-management/