Federal Tax Day - Current, I.4, Fourth Quarter 2026 Interest Rates Remain Unchanged (Rev. Rul. 2026-15; IR 2026-98), (Aug 24, 2026)

The over and underpayment interest rates for the fourth quarter of 2026 remain unchanged. The fourth quarter begins on October 1, 2026. The rates will be:

• 7 percent for overpayments

• 6 percent for corporate overpayments

• 7 percent for underpayments, and

• 9 percent for large corporate underpayments.

The interest rate for the part of a corporate overpayment exceeding $10,000 is 4.5 percent.

Computation of Fourth Quarter 2026 Interest Rates

The IRS computes these interest rates quarterly. The fourth quarter rates are based on the federal short-term rate for July 2026 which is 4 percent.

For noncorporate taxpayers:

• the overpayment rate is the short-term rate plus 3 percent, and

• the underpayment rate is the short-term rate plus 3 percent.

For corporate taxpayers:

• the underpayment rate is the short-term rate plus 3 percent

• the overpayment rate is the federal short-term rate plus 2 percent.

• the rate on the part of a corporate overpayment that exceeds $10,000 for a tax period is the short-term rate plus 0.5.

• the underpayment rate for large corporations is 9 percent.

Rev. Rul. 2026-15

IR 2026-98