Modvat credit reversal required when inputs are written off; officers must conduct timely checks to prevent misuse. Assessees must immediately reverse Modvat credit taken on inputs that have been written off for stock purposes and notify the concerned Range Officers; failure to reverse or delayed reversal constitutes misuse of the Modvat scheme. Central Excise Range Officers, Audit and Preventive parties are directed to conduct timely checks and inform field formations to prevent revenue leakage.