In the case of an article sold otherwise than at arm's length, and at less than fair market price, the constructive sale price shall be the price for which such articles are sold, in the ordinary course of trade, by manufacturers or producers thereof, as determined by the Secretary. Once such a constructive sale price has been determined, no further adjustment of such price shall be made. See sections 4216(b) (3), (4), and (5), and § 48.4216 (b)-4 , for specific methods for determining constructive sale prices for intercompany sales under certain defined conditions.
26 C.F.R. §48.4216(b)-2