When Project parameter / All Projects – Journals – Require Activity is marked as Yes for all Journals except Item, Project – Purchase order on a Procurement category, is allowed to be created and Invoice posted without an Activity id mentioned on it. Procurement category is an expense and hence the error should trigger as Expense is marked. As this was concluded as a missing design as all PO as considered Item transactions - we should have a 4th Field in the Journals - Require Activity for Procurement category.