26 CFR 55.6001-1: -1 Notice or regulations requiring records, statements, and special returns.

(a) In general. Any person subject to tax under Chapter 44 of the Code shall keep such complete and detailed records as are sufficient to enable the district director to determine accurately the amount of liability under Chapter 44.

(b) 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 Chapter 44.

(c) Retention of records. The 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.