Retrospective amendment to CENVAT credit rules validates prior credit adjustments and sets specific recovery and instalment procedures. The amendment retrospectively modifies the Explanation in rule 3(6)(b) of the CENVAT Credit Rules, 2002, validating past actions taken under it and confirming retrospective rulemaking power; it allows allowance of CENVAT credit for additional duty under the Additional Duties Act where previously disallowed, mandates recovery where credit would not have been available if amendment had been in force, and prescribes a modified recovery framework including notices, declarations, officer determinations, interest computation, and instalment payment procedures while clarifying non punitive effect and the definition of CENVAT credit.