Input tax credit on second-hand goods requires prescribed seller invoice or cash memo; absence bars credit claim. Input tax credit on second hand goods from an unregistered resident seller is allowed only where the registered dealer holds an invoice or receipt signed by that seller showing the goods' description, amount paid, seller's name and address, and the seller's PAN if any, and further only where the dealer possesses the original invoice or cash memo issued under the Act (or the former Delhi Sales Tax Act) evidencing the resident seller's purchase of the goods in Delhi.