27 C.F.R. § 46.102
(b) Application for employer identification number. Each taxpayer who files a special tax return and who has not already been assigned an employer identification number must file Internal Revenue Service (IRS) Form SS-4 to apply for one. The taxpayer must apply for and be assigned only one employer identification number, regardless of the number of places of business for which the taxpayer is required to file a special tax return. The taxpayer must apply for the employer identification number no later than 7 days after the filing of the taxpayer's first special (occupational) tax return. IRS Form SS-4 may be obtained from the director of an IRS service center, from any IRS district director, or from https://www.irs.gov.
(26 U.S.C. 6109)
[T.D. TTB-79, 74 FR 37420, July 28, 2009, as amended by T.D. TTB-196, 89 FR 87950, Nov. 6, 2024]