IDX stands for "Internet Data Exchange" commonly called Broker Reciprocity. The next stage in the evolution of the MLS, IDX is the primary means of enhancing cooperation between agents to facilitate the purchase and sale of property and alike lettings. IDX gives MLS Participants the tool they need to display each others' listings on their Internet websites. Under the IDX INEA system, agents exchange consent to display each others listings on the Internet. You have full control over which property listings you display.
6/ Guidance for property sales businesses – an overview
7/ OFT Guidance PDF on the Requirements of Consumer Law/Definition of Estate Agency Work ( October 2013)