The SEC has proposed a rule amendment to shorten the standard settlement cycle for most broker-dealer securities transactions from three business days after the trade date (T+3) to two business days after the trade date (T+2). The proposed amendment is designed to reduce the risks that arise from the value and number of unsettled securities transactions prior to the completion of settlement, including credit, market, and liquidity risk directly faced by U.S. market participants. 

For more information about the proposal see:  https://www.sec.gov/news/pressrelease/2016-200.html