Account assignment mandatory for RTP material


When i'm creating PO for RTP material . i'm getting an error "Account assignment mandatory for material 101010 (enter acc. ***. cat.)"

Actually i have created a po with raw material with ROH and returnables with LEER as material type.

IN po, line item 1 for ROH material and Line item 2 for LEER mat type and ticked return indicator . where i 'm getting a error the abv error ,

why its giving and how to solve it...