The FTB has announced the adjusted interest rate for the period January 1, 2021, through June 30, 2021. (R&TC §19521) The compounded daily rate for personal income tax underpayments and overpayments and corporate income and franchise tax underpayments is 3%. The rate for corporation tax overpayments for the period is 0%. Those rates for the current period of July 1, 2020, through December 31, 2020, are 5% and 2% respectively.
To see current and historical rates, go to: www.caltax.com/research/ftb-interest-rates/