Mortgage-backed securities in the United States are generally traded on a "to-be-announced," or TBA, basis. The key feature of a TBA trade is that the identity of the securities to be delivered to the buyer is not specified exactly at the time of the trade, facilitating a liquid forward market....

Mortgage-backed securities in the United States are generally traded on a “to-be-announced,” or TBA, basis. The key feature of a TBA trade is that the identity of the securities to be delivered to the buyer is not specified exactly at the time of the trade, facilitating a liquid forward...