Closing refers to the end of a trading session or the end of a trading day, at which point all open positions must either be closed or carried over to the next trading session. The closing price is the last price at which an asset was traded at the end of a trading session or day. The closing price is used to calculate daily price changes and to mark-to-market open positions. In forex trading, the closing of a position refers to the action of selling a currency that has been previously bought, or buying back a currency that has been previously sold.