IRS Hiking Interest Rates on Oct. 1

The IRS said Friday that interest rates will go up for the fourth quarter of 2023, which begins on Oct. 1.

The last time the agency increased interest rates was for the first quarter of this year when the rate for tax overpayments and underpayments was 7% per year, compounded daily, up from 6% for Q4 2022. Interest rates had stayed the same in Q2 and Q3 of this year.

Here is a complete list of the new rates for Q4 2023:

8% for overpayments (payments made in excess of the amount owed), 7% for corporations.
5.5% for the portion of a corporate overpayment exceeding $10,000.
8% for underpayments (taxes owed but not fully paid).
10% for large corporate underpayments.

Under the Internal Revenue Code, the rate of interest is determined on a quarterly basis. For taxpayers other than corporations, the overpayment and underpayment rate is the federal short-term rate plus 3 percentage points.

Generally, in the case of a corporation, the underpayment rate is the federal short-term rate plus 3 percentage points, and the overpayment rate is the federal short-term rate plus 2 percentage points. The rate for large corporate underpayments is the federal short-term rate plus 5 percentage points. The rate on the portion of a corporate overpayment of tax exceeding $10,000 for a taxable period is the federal short-term rate plus one-half (0.5) of a percentage point.

The interest rates announced on Aug. 25 are computed from the federal short-term rate determined last month. See Revenue Ruling 2023-17 for details.