Limitation on excise recovery: amended extended period applies prospectively and cannot revive already time barred demands. The amendment extended the limitation for issuing show cause notices for recovery of unpaid or short levied excise duty from six months to one year. It applies prospectively: if the original six month limitation expired before the amendment's commencement the extended period cannot be used; if the six month period expires on or after commencement, notices may be issued within the one year period from the relevant date. Field formations must apply the amendment only to cases where limitation runs on or after commencement and not revive already time barred demands.