26 CFR § 1.6001-1 - Records.
(a) In general. Except as provided in paragraph (b) of this section, any person subject to tax under subtitle A of the Code (including a qualified State individual income tax which is treated pursuant to section 6361(a) as if it were imposed by chapter 1 of subtitle A), or any person required to file a return of information with respect to income, shall keep such permanent books of account or records, including inventories, as are sufficient to establish the amount of gross income, deductions, credits, or other matters required to be shown by such person in any return of such tax or information.
(b) Farmers and wage-earners. Individuals deriving gross income from the business of farming, and individuals whose gross income includes salaries, wages, or similar compensation for personal services rendered, are required with respect to such income to keep such records as will enable the district director to determine the correct amount of income subject to the tax. It is not necessary, however, that with respect to such income individuals keep the books of account or records required by paragraph (a) of this section. For rules with respect to the records to be kept in substantiation of traveling and other business expenses of employees, see § 1.162–17.
(c) Exempt organizations. In addition to such permanent books and records as are required by paragraph (a) of this section with respect to the tax imposed by section 511 on unrelated business income of certain exempt organizations, every organization exempt from tax under section 501(a) shall keep such permanent books of account or records, including inventories, as are sufficient to show specifically the items of gross income, receipts and disbursements. Such organizations shall also keep such books and records as are required to substantiate the information required by section 6033. See section 6033 and §§ 1.6033–1 through 1.6033–3.
(d) Notice by district director requiring returns statements, or the keeping of records. The district director may require any person, by notice served upon him, to make such returns, render such statements, or keep such specific records as will enable the district director to determine whether or not such person is liable for tax under subtitle A of the Code, including qualified State individual income taxes, which are treated pursuant to section 6361(a) as if they were imposed by chapter 1 of subtitle A.
(e) Retention of records. The books or records required by this section shall be kept at all times available for inspection by authorized internal revenue officers or employees, and shall be retained so long as the contents thereof may become material in the administration of any internal revenue law.