Remission of duty for destroyed or unfit excisable goods requires supervised destruction and compliance with prescribed procedural safeguards. Rule 21 permits remission of duty where excisable goods are lost, destroyed by accident, or declared unfit prior to removal, with graded delegation of remission and supervision powers to competent officers. Applications require supporting proof, prompt processing, possible laboratory testing, physical verification and supervised destruction that renders goods irretrievable. Supervising officers must endorse records and certify destruction; CENVAT credit on inputs in destroyed goods must be reversed. No remission for theft; Commissioners may remit without limit but must report significant cases.