Revenue Ruling 2021-04 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.

Revenue Ruling will be in IRB:  2021-06, dated February 8, 2021.

Notice 2021-09 provides guidance on the corporate bond monthly yield curve, the corresponding spot segment rates used under § 417(e)(3), and the 24-month average segment rates under § 430(h)(2) of the Internal Revenue Code.  In addition, this notice provides guidance as to the interest rate on 30-year Treasury securities under § 417(e)(3)(A)(ii)(II) as in effect for plan years beginning before 2008 and the 30-year Treasury weighted average rate under § 431(c)(6)(E)(ii)(I), as reflected by the application of § 430(h)(2)(C)(iv). 

Notice 2021-09 will be in IRB:   2021-5, dated February 1, 2021.