Job work exemption permits excise free manufacture of specified goods subject to supplier undertaking and prescribed usage conditions. Exemption from whole excise duty applies to specified goods manufactured as job work when the supplier gives an undertaking to the proper officer that goods received from the job worker will be used by the supplier in or in relation to the manufacture of exempt specified goods or listed articles, and that the supplier will pay excise duty if he fails to do so. Waste or by products are exempt if used by the job worker in manufacture or returned to and used by the supplier. 'Job work' means processing supplied raw or semi finished goods to complete part or all of the manufacturing process or any essential operation.