Modvat credit controls: duplicate invoices required; verify and penalise double credits and invoice falsification. The Board warns that duplicate invoices are the prescribed basis for claiming Modvat credit and that original invoices may be used only exceptionally when duplicates are lost in transit with Assistant Collector approval. It directs immediate verification to detect credits taken on originals or double credits arising from falsified documents, and mandates action against both suppliers and recipients where improper credits are found, with instructions to field formations to ensure strict scrutiny and penal measures.