27 C.F.R. § 20.265
(a) Any person required to keep records under this part shall retain copies of invoices which will enable appropriate TTB officers to readily obtain the details regarding:
(b) The appropriate TTB officer may, on application filed by the permittee, waive the requirements for retaining invoices if the quantity sold to any person during a calendar month does not exceed 25 gallons, and if a waiver will not hinder the effective administration of this part and will not pose a jeopardy to the revenue.
(Approved by the Office of Management and Budget under control number 1513-0061)
[T.D. ATF-199, 50 FR 9162, Mar. 6, 1985, as amended by T.D. TTB-140, 81 FR 59456, Aug. 30, 2016]