Part III. Administrative, Procedural, and Miscellaneous

except for farmers and wage-earners, any person subject to income tax, or any person required to file a return of information with respect to income, must keep such books and records, including inventories, as are sufficient to establish the amount of gross income, deductions, credits, or other matters required to be shown by that person in any return of such tax or information.

.03 Section 1.6001–1(e) provides that the books or records required by § 6001 must be kept available at all times for inspection by authorized internal revenue officers or employees, and must be retained so long as the contents thereof may become material in the administration of any internal revenue law.