47 C.F.R. § 43.21
Transactions with affiliates
(a)-(d) [Reserved]
(e) Each incumbent local exchange carrier, except mid-sized incumbent local exchange carriers, as defined by § 32.9000 with annual operating revenues equal to or above the indexed revenue threshold shall file, no later than April 1 of each year:
(1) Its revenues, expenses and investment for all accounts established in part 32 of this chapter, on an operating company basis,
(2)-(3) [Reserved]
(f)-(k) [Reserved]