15B. Non-reversal of CENVAT credit.Where an assessee has paid duty of excise on a final product and has been allowed credit of the duty or tax or cess paid on inputs, capital goods and input services used in making of the said product, but subsequently the process of making the said product is held by the court as not chargeable to excise duty, the Central Government may, by notification, order for non-reversal of such credit allowed to the assessee subject to such conditions as may be specified in the said notification Provided that the order for non-reversal of credit shall not apply where an assessee has preferred a claim for refund of excise duty paid by him Provided further that the Central Government may also specify in the notification referred to above for non-reversal of credit, if any, taken by the buyer of the said product.