Item category & can only be used with material

Message type: E = Error

Message class: ME - Purchasing: General Messages

Message number: 018

Message text: Item category & can only be used with material



What causes this issue?

The <GL:item_category>item category</> you entered requires the entry
of a <GL:material number>material number</>.


How to fix this error?

Enter a valid material number.

Error message extract from SAP system. Copyright SAP SE.