Settlement Date is a securities industry term explaining the date on which a trade (bonds, commodities, equities, foreign exchange, etc.) settles. That is, the definite day on which transfer of cash or assets is completed.
It is not essentially the same as value date (when the settlement amount is calculated). For example, the back office may require a few days to make payment. This gap (among valuation and settlement) is often written into the financial contract, although the actual settlement date can as well differ from that originally specified due to problems or errors. It is occasionally considered to as Contractual Settlement Date.