Since 1975, federal firearms licensees have been required by regulation (1) and subsequently by law (2) to report all transactions in which an unlicensed person has acquired two or more pistols and/or revolvers at one time or during any 5 consecutive business days (called a multiple sale).
(1) 27 C.F.R. 178.126a.
(2) See 18 U.S.C. 923(g)(3)(A). The provision states, “Each licensee shall prepare a report of multiple sales or other dispositions whenever the licensee sells or otherwise disposes of, at one time or during any five consecutive business days, two or more pistols, or revolvers, or any combination of pistols and revolvers totalling two or more, to an unlicensed person. The report shall be prepared on a form specified by the Secretary [of the Treasury] and forwarded to the office specified thereon and to the department of State police or State law enforcement agency of the State or local law enforcement agency of the local jurisdiction in which the sale or other disposition took place, not later than the close of business on the day that the multiple sale or other disposition occurs.”