The Pennsylvania Department of Revenue has announced that for the calendar year beginning January 1, 2017, the interest rate for the underpayment of tax is 4% per annum.  The interest rate for the overpayment of personal income tax is 4% per annum.  Overpayment of other taxes will be subject to an interest rate of 2% per annum.  The notice can be viewed on the department’s website at  PA Bulletin Doc. No. 16-2268, Pennsylvania Department of Revenue, December 24, 2016. Continue Reading.