Is not later than 90 days after the close of such taxable year of any such corporation, then such return with such schedule or schedules may be filed, or any such schedule or schedules may be filed, on the basis of estimates of amounts or percentages (for any such taxable year of any such corporation) required to be shown on any such schedule or schedules. If any such estimate differs from the actual amount or percentage, the taxpayer shall, within 90 days after the close of any such taxable year of any such corporation, file (or attach to a claim for refund or amended return filed) at the office of the district director with whom he filed the return a new schedule or schedules showing the actual amounts or percentages.
26 C.F.R. §1.1248-7