In Purchasing contract you will receive this error
SAP Business ByDesign
When item type is either material or service then product Id is mandatory though you have Product category already maintained.
So you can either enter Product ID or change item type to Product category.
Product ID missing; enter product ID or product category ID
KBA , AP-PCP-PCT , Purchasing Contract , AP-RFQ , RFQ Processing , AP-POP , Purchase Order Processing , Problem