# Treas. Reg. § 41.6109-1: Identifying numbers.

Source: eCFR as of 2026-10-19 <https://www.ecfr.gov/current/title-26/section-41.6109-1>. Interprets 26 U.S.C. § 6109.

Every person required under § 41.6011(a)-1 to make a return must provide the identifying number required by the instructions to the form on which the return is made. 

[T.D. 8879, 65 FR 17155, Mar. 31, 2000]