Item category & can only be used without material

Message type: E = Error

Message class: ME - Purchasing: General Messages

Message number: 019

Message text: Item category & can only be used without material



What causes this issue?

The <GL:item_category>item category</> you entered does not permit the
entry of a <GL:material_number>material number</>.


How to fix this error?

Set the material number to "blank".

Error message extract from SAP system. Copyright SAP SE.