26 C.F.R. § 601.101

(a) General. The Internal Revenue Service is a bureau of the Department of the Treasury under the immediate direction of the Commissioner of Internal Revenue. The Commissioner has general superintendence of the assessment and collection of all taxes imposed by any law providing internal revenue. The Internal Revenue Service is the agency by which these functions are performed. Within an internal revenue district the internal revenue laws are administered by a district director of internal revenue. The Director, Foreign Operations District, administers the internal revenue laws applicable to taxpayers residing or doing business abroad, foreign taxpayers deriving income from sources within the United States, and taxpayers who are required to withhold tax on certain payments to nonresident aliens and foreign corporations, provided the books and records of those taxpayers are located outside the United States. For purposes of these procedural rules any reference to a district director or a district office includes the Director, Foreign Operations District, or the District Office, Foreign Operations District, if appropriate. Generally, the procedural rules of the Service are based on the Internal Revenue Code of 1939 and the Internal Revenue Code of 1954, and the procedural rules in this part apply to the taxes imposed by both Codes except to the extent specifically stated or where the procedure under one Code is incompatible with the procedure under the other Code. Reference to sections of the Code are references to the Internal Revenue Code of 1954, unless otherwise expressly indicated.

(b) Scope. This part sets forth the procedural rules of the Internal Revenue Service respecting all taxes administered by the Service, and supersedes the previously published statement (26 CFR (1949 ed., Part 300-End) Parts 600 and 601) with respect to such procedural rules. Subpart A provides a descriptive statement of the general course and method by which the Service's functions are channeled and determined, insofar as such functions relate generally to the assessment, collection, and enforcement of internal revenue taxes. Certain provisions special to particular taxes are separately described in Subpart D of this part. Conference and practice requirements of the Internal Revenue Service are contained in Subpart E of this part. Specific matters not generally involved in the assessment, collection, and enforcement functions are separately described in Subpart B of this part. A description of the rule making functions of the Department of the Treasury with respect to internal revenue tax matters is contained in Subpart F of this part. Subpart G of this part relates to matters of official record in the Internal Revenue Service and the extent to which records and documents are subject to publication or open to public inspection. This part does not contain a detailed discussion of the substantive provisions pertaining to any particular tax or the procedures relating thereto, and for such information it is necessary that reference be made to the applicable provisions of law and the regulations promulgated thereunder. The regulations relating to the taxes administered by the Service are contained in title 26 of the Code of Federal Regulations.