IRS interest rates increase for the second quarter of 2022 beginning April 1.
The regular non-corporate underpayment and overpayment interest rates are 4%.
IRS personnel often refer to the regular underpayment or overpayment interest rate as "R% interest" or "stat interest", to encompass the different quarterly regular underpayment or overpayment interest rates that might apply within a specific interest computation period.