interpositioning investment & finance definition

The involvement of a third party between a broker-dealer and the best available market price that results in the customer paying a bigger markup or markdown than would have been the case if the third party had not been present. For example, Dealer A satisfies a customer order to buy a security by purchasing the security through Dealer B who in turn purchases the security from the market maker. Dealer B marks up the security to Dealer A, who then marks up the security again when selling it to the customer. Interpositioning is considered unethical by the National Association of Securities Dealers.