The privilege of filing consolidated returns is extended to all includible corporations constituting affiliated groups as defined in section 1504. See the regulations under Sec. 1.1502 for a description of an affiliated group and the corporations which may be considered as includible corporations. [T.D. 6500, 25 FR 12106, Nov. 26, 1960] Secs. 1.1504-2--1.1504-3 [Reserved]