NOT ABLE TO CREATE INVOICE

Hi SAP Gurus

Created return order

Created Retrun Delivery

fully picked

only one line time is there

ZERE ( Order type )

ZERN ( Item category)

ZERC biling type

ERROR Message

" Item number 10 Item category ZERE ZREN cannot be invoice with billing type ZERC"

Could you please tell me what could be the reason behind this?

Thanks & Regards,

SPRaju