An agent that mediates sales and exchanges between securities buyers and sellers at even lower commission rates than those offered by a regular discount broker. As one might expect, deep discount brokers also provide fewer services to clients than standard brokers; such brokers typically provide little more than the fulfillment of stock and option trades, charging a flat fee for each. Taobiz explains Deep Discount Broker With the advent of online trading, deep discount brokers have grown more and more popular. Even older, established brokerage houses have added deep discount broker services to their list of financial service offerings.