P.O Creation for MTL group wise

Dear

When i create P.O , With Mtl group ref & W/O mtl no - the Error msg as follows.

Please enter material number or account assignment category

Message no. 06026

Diagnosis

You have entered neither the material number nor the account assignment

category in the item. An item representing a material without a master

record (i.e. no material number is specified) or a service must have an

account assignment category.

Procedure

Enter a valid material number.

If you wish to procure a material without a master record or a service,

enter a suitable account assignment category for the item.

Regards,

Suresh.p