The daily reference exchange rate is set at 23,144 VND per USD on January 21 (Photo: VNA) Hanoi (VNA) - The State Bank of Vietnam set the daily reference exchange rate at 23,144 VND per USD on January 21, down 4 VND from the previous day. With the current trading band of +/-3 percent, the ceiling rate applied to commercial banks during the day is 23,838 VND/USD and the floor rate, 22,450 VND/USD. The opening hour rates at some commercial banks slightly increased. At 8:25 am, Vietcombank listed the buying rate at 23,955 VND/USD and the selling rate at 23,165 VND/USD, both up 5 VND from January 20.