Balancing Field Business Area in Line 001 Not Filled

In SAP Concur, we get this error message: Balancing Field "Business Area" in line item 001 not filled. Is this error in Concur or in SAP? What needs to be updated / checked in order to be able to post the expense report. No knowlege of SAP sits within the Concur Admin team so please use laymen's terms. Thank you .