Revenue Ruling 2024-18 provides the fourth quarter interest rates for 2024, including the rates for underpayments and overpayments. The rates for interest determined under Section 6621 of the code for the calendar quarter beginning October 1, 2024, will be 8 percent for overpayments (7 percent in the case of a corporation), 8 percent for underpayments, and 10 percent for large corporate underpayments. The rate of interest paid on the portion of a corporate overpayment exceeding $10,000 will be 5.5 percent. 

Revenue Ruling 2024-18 will be in IRB:  2024-37, dated September 9, 2024.