Credit means claim of set-off of something paid earlier. Cenvat credit means use of excise duty, service tax and custom duty (which is paid on input, input services and capital goods) paid earlier against service tax and excise duty payable on rendering of services and clearance of manufacturing of goods. Cenvat Credit Rules 2004 deals with credit of service tax and excise duty. It means service tax and excise duty are interchangeable ie. to pay excise duty one can use the input of service tax or input excise and vice versa.