Revenue Ruling 2020-18 provides the rates for interest determined under Section 6621 of the code for the calendar quarter beginning October 1, 2020, will be 3 percent for overpayments (2 percent in the case of a corporation), 3 percent for underpayments, and 5 percent for large corporate underpayments. The rate of interest paid on the portion of a corporate overpayment exceeding $10,000 will be 0.5 percent.

Revenue Ruling 2020-18 will be published in Internal Revenue Bulletin 2020-39 on Sept. 21, 2020