Charging excise@12.5% on billing from depot

Dear Sir, we have a Stock & Sales Point in Mumbai where as Plant is in Bhiwadi (Raj). we have been doing Stock transfer at Maximum Qty Sold rate during Month or take reference of prevailing/Billing price at or around transfer date . My query is if we bill higher than transfer rate but pass excise based on our transfer price , can excise deptt. raise question on Loss of Revenue as it will be a recurring exercise (even if Qty is less than 50% of total supply). kindly guide ,what should be the ideal practice & procedure for long term & substantial sales planning. with best regards B KJHA