27 C.F.R. § 31.95 – Caterers.

(a) General. When a contract to furnish liquors is made by a caterer at a place of business for which the caterer has registered under this part, no additional registration is required by virtue of the serving of the liquors at a different location.
(b) Additional registration. When the contract of a caterer provides for the sale of liquors by the drink at a place, or simultaneously at different places, other than the place of business for which the caterer has registered under this part, a separate registration is required for each such place if the caterer does not keep the records specified in paragraph (c) of this section.
(c) Records. Caterers must maintain sufficient commercial records to identify all locations where activities subject to registration occur. These commercial records must indicate the names and addresses of locations where alcoholic beverages have been sold or offered for sale and the dates and times that those activities occurred. These commercial records must be available to an appropriate TTB officer upon request.
(26 U.S.C. 5121, 5122)