issue in creating billing without reference

Hi,

My requirement is to create billing document without reference .I am using the BAPI -BAPI_BILLINGDOC_CREATEMULTIPLE to create billing document .The following are the fields which I am paains to BAPI.

SALES ORG

DIST CHANN

DIVISION

DOC_TYPE - CR

BILLING TYPE -G2

SOLD to-

ITEM CATEGORY- ZG2N

PLANT

MATERIAL

QUANTITY

SHIP TO

But I am getting following information message which is not creating billing document.

VF-I-044-The item is not relevant for billing.

Can anyone please help on this. Its very urgent.If anyone provide the sample code it is appreciated.

Thanks,

Akshatha