26 C.F.R. § 20.6601-1
Interest on underpayment, nonpayment, or extensions of time for payment, of tax
For regulations concerning interest on underpayments, etc., see § 301.6601-1 of this chapter (Regulations on Procedure and Administration).
For regulations concerning interest on underpayments, etc., see § 301.6601-1 of this chapter (Regulations on Procedure and Administration).