Tokyo Overnight Average Rate (TONA rate or TONAR) or Japanese Yen Uncollateralized Overnight Call Rate () is an unsecured interbank overnight interest rate and reference rate for Japanese yen. Mutan rate and TONA rate are the same things.
Japanese yen uncollateralized overnight call market started in July 1985.
Since December 28, 2016, the Bank of Japan has recommended the TONA rate as the preferred Japanese yen risk-free reference rate.
TONA rate is recommended as a replacement for Japanese yen LIBOR, which was phased out at the end of 2021, and Euroyen TIBOR, which will be terminated at the end of 2024.