The Internal Revenue Service (IRS) announced today that interest rates for tax overpayments and underpayments will remain unchanged for the calendar quarter beginning October 1, 2026. This decision maintains the current rates for individuals and corporations, which are determined quarterly based on the federal short-term rate.
For individuals, both overpayments and underpayments will continue to accrue interest at 7% per year, compounded daily. Corporations will see a 6% rate for overpayments, dropping to 4.5% for the portion of an overpayment exceeding $10,000. Corporate underpayments will be charged 7%, while large corporate underpayments will incur a 9% rate.
These rates are calculated from the federal short-term rate determined in July 2026. The specific details are outlined in Revenue Ruling 2026-15, which is set to appear in Internal Revenue Bulletin 2026-36, dated August 31, 2026.