The term "fully paid securities" refers to securities held in a customer's margin or cash account that have been completely paid for and are not being pledged as collateral to support the purchase of other securities on margin. The term is relevant from a regulatory perspective as the SEC requires that U.S. broker dealers segregate and maintain in a good control location (e.g., DTC or bank) all customer securities which are fully paid.  Such securities cannot be pledged or loaned to finance the activities of the firm or other customers.

Note that securities which were fully paid at the date of acquisition may later be reclassified as margin or excess margin securities based upon the customer's subsequent trade and/or borrowing activity. For example, if the loan value of fully paid securities is subsequently used to acquire additional securities on credit, a portion of securities will then be classified as margin securities and subject to a lien and potential pledge or hypothecation by the broker.

See also "excess margin securities".