The Mutan interest rate is the un-collateralized overnight call rate in Japan. It is the reference rate for JPY overnight unsecured transactions in the Japanese market. It was launched in July 1985[1] and it is the main tool for the transmission of the Bank of Japan's monetary policy. Mutan rate and TONA rate are the same things.
Bank of Japan publishes a provisional rate, rounded to three decimal places,[2] every business day around 17:15 JST (or 18:15 JST for the last business day of the month).[3] A final result is published the following business day around 10:00 JST. The results published contain weighted-average, highest, and lowest rate during the business day.[4]