We currently have an issue where a supplier creates a service invoice against a service purchase order, but the Service Start Date and Service End Date fields for service line items are not visible at the header level.

You need to enable the following Business Network (BN) Rule to be able to see Service Start Date and Service End Date at the header level.

Allow suppliers to send invoices with service information

After enabling the above rule in BN, vendors can see Service Start Date and Service End Date at the header level.

Invoicing > Service Invoicing