Revenue Ruling 2021-12 provides various prescribed rates for federal income tax purposes including the applicable federal interest rates, the adjusted applicable federal interest rates, the adjusted federal long-term rate, and the adjusted federal long-term tax-exempt rate. These rates are determined as prescribed by § 1274. 

The rates are published monthly for purposes of sections 42, 382, 412, 642, 1288, 1274, 7520, 7872, and various other sections of the Internal Revenue Code.

It will appear in IRB 2021-27 dated July 6, 2021.