To filter data entity using an enum field, we need to use a specific query expression syntax. For example, to filter Purchase order header data entity, PurchaseOrderHeadersV2, to get only ‘Confirmed’ purchase orders, we can add filter to DocumentApprovalStatus entity field which sources its value from VersioningDocumentState enum like below: https://usnconeboxax1aos.cloud.onebox.dynamics.com/data/PurchaseOrderHeadersV2?$filter=DocumentApprovalStatus eq Microsoft.Dynamics.DataEntities.VersioningDocumentState’Confirmed’ As you can see below the query filter successfully filters Purchase order header entity to get only ‘Confirmed’ purchase orders: