Below are links to the pages located under the tab, "Regulations."
"A regulation is issued by the Internal Revenue Service and Treasury Department to provide guidance for new legislation or to address issues that arise with respect to existing Internal Revenue Code sections. Regulations interpret and give directions on complying with the law." (IRS website)
Both proposed regulations and final rules are published in the Federal Register and final regulations are codified in the Code of Federal Regulations. In addition, they are "printed . . .[u]nder the heading "Treasury Decisions " (T.D.) in the Internal Revenue Bulletins (I.R.B.), . . . [and] in the Cumulative Bulletin (C.B.)." (Publication of Regulations, IRM § 4.10.7.2.3.5)