The Internal Revenue Service today announced that interest rates will decrease for the calendar quarter beginning Oct. 1, 2011. The rates will be:

. Three (3) percent for overpayments [two (2) percent in the case of a corporation];
. Three (3) percent for underpayments;
. Five (5) percent for large corporate underpayments; and
. Zero and one-half (0.5) percent for the portion of a corporate overpayment exceeding $10,000.

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 today are computed from the federal short-term rate during July 2011 to take effect Aug. 1, 2011, based on daily compounding.

Revenue Ruling 2011-18, announcing the rates of interest, is attached and will appear in Internal Revenue Bulletin No. 2011-39, dated Sept. 26, 2011.