Mississippi Code
Article 3 - Withholding of Tax
§ 27-7-333. Employer's withholding account number

Except as otherwise provided in this section, every employer, as defined herein, shall, on or before January 1, 1969, make application to the commissioner for and be assigned an employer's withholding account number. The account number assigned to an employee shall be used by such employer on all returns, reports and inquiries addressed to the commissioner.
This section shall not apply to an "out-of-state business" during a "disaster response period" as such terms are defined in Section 27-113-5.