26 CFR § 1.6109-1 - Identifying numbers.
---
identifier: "/us/cfr/t26/s1.6109-1"
source: "ecfr"
legal_status: "authoritative_unofficial"
title: "26 CFR § 1.6109-1 - Identifying numbers."
title_number: 26
title_name: "Internal Revenue"
section_number: "1.6109-1"
section_name: "Identifying numbers."
chapter_name: "INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY"
subchapter_number: "A"
subchapter_name: "INCOME TAX"
part_number: "1"
part_name: "INCOME TAXES"
positive_law: false
currency: "2026-03-24"
last_updated: "2026-03-24"
format_version: "1.1.0"
generator: "[email protected]"
authority: "26 U.S.C. 7805, unless otherwise noted."
regulatory_source: "T.D. 6500, 25 FR 11402, Nov. 26, 1960; 25 FR 14021, Dec. 21, 1960; T.D. 9989, 89 FR 17606, Mar. 11, 2024, unless otherwise noted."
cfr_part: "1"
---
# 1.6109-1 Identifying numbers.
(a) *Information to be furnished after April 15, 1974.* For provisions concerning the requesting and furnishing of identifying numbers with respect to returns, statements, and other documents which must be filed after April 15, 1974, see § 301.6109-1 of this chapter (Regulations on Procedure and Administration).
(b) *Information to be furnished before April 15, 1974.* For provisions concerning the requesting and furnishing of identifying numbers with respect to returns, statements, and other documents which must be filed before April 16, 1974, see 26 CFR § 1.6109-1 (revised as of April 1, 1973).
[T.D. 7306, 39 FR 9946, Mar. 15, 1974; 39 FR 11080, Mar. 25, 1974]