An independent corporation owned by broker/dealers and banks responsible for: (l) holding deposit securities owned by broker/dealers and banking institutions; ( 2) arranging the receipt and delivery of securities between users by means of debiting and crediting their respective accounts; (3) arranging for payment of monies between users in the settlement of transactions. The DTC is generally used by option writers because it guarantees delivery of underlying securities if assignment is made against securities held in DTC.