Rev. Rul. 2026-15, page 216.

Interest rates: underpayments and overpayments. The rates for interest determined under Section 6621 of the code for the calendar quarter beginning October 1, 2026, will be 7 percent for overpayments (6 percent in the case of a corporation), 7 percent for underpayments, and 9 percent for large corporate underpayments. The rate of interest paid on the portion of a corporate overpayment exceeding $10,000 will be 4.5 percent.

T.D. 10053, page 237. These final regulations amend regulations under section 3406 to change the threshold for when certain third party settlement organizations (TPSOs) are required to perform backup withholding. These final regulations clarify that in the case of certain payments made through third parties, the amount subject to backup withholding under section 3406 is determined by taking into account the exception for de minimis payments by TPSOs in section 6050W(e). These final regulations also clarify the amount subject to backup withholding and clarify situations when the threshold does not apply. The final regulations reflect recent changes to the statutory law.

Finding Lists begin on page ii.