Electronic securities marketplace having integration with order management systems

A computer-implemented method comprising:

• accessing, by an electronic marketplace, records of open orders in a database of an order management system;
• determining that at least one of the open orders from the database of the order management system has been, at least partly, fulfilled;
• in response to determining that the at least one of the open order has been, at least partly, fulfilled, providing an indication of at least one of a complementary service and a complementary product available through the marketplace.