For example, M, a private foundation, first has excess business holdings in X, a corporation, on February 5, 1972. A notice of deficiency is mailed under section 6212 to M on June 1, 1974. With respect to M's excess business holdings in X, the taxable period begins on February 5, 1972, and ends on June 1, 1974.
26 C.F.R. §53.4943-9