Section 31.6109-1 - Supplying of identifying numbers(a)In general. The returns, statements, and other documents required to be filed under this subchapter shall reflect such identifying numbers as are required by each return, statement, or document and its related instructions. See § 301.6109-1 of this chapter (Regulations on Procedure and Administration).(b)Effective date. The provisions of this section are effective for information which must be furnished after April 15, 1974. See 26 CFR § 31.6109-1 (revised as of April 1, 1973) for provisions with respect to information which must be furnished before April 16, 1974.39 FR 9946, Mar. 15, 1974