20 CFR §404.1220

1. (a)State and local governments. When a State submits a modification to its agreement under section 218 of the Act, which extends coverage to periods prior to 1987, SSA will assign a special identification number to each political subdivision included in that modification. SSA will send the State a Form SSA-214-CD, “Notice of Identifying Number,” to inform the State of the special identification number(s). The special number will be used for reporting the pre-1987 wages to SSA. The special number will also be assigned to an interstate instrumentality if pre-1987 coverage is obtained and SSA will send a Form SSA-214-CD to the interstate instrumentality to notify it of the number assigned.
2. (b)Coverage group number for coverage groups. If a State's agreement provides coverage for a State or a political subdivision based on designated proprietary or governmental functions, the State shall furnish a list of those groups. The list shall identify each designated function and the title and business address of the official responsible for filing each designated group's wage report. SSA assigns a coverage group number to each designated group based on the information furnished in the list.
3. (c)Unit numbers for payroll record units. SSA assigns, at a State's request, unit numbers to payroll record units within a State or political subdivision. When a State requests separate payroll record unit numbers, it must furnish the following:
   1. (1)The name of each payroll record unit for the coverage group; and
   2. (2)The title and business address of the official responsible for each payroll unit.
4. (d)Unit numbers where contribution amounts are limited—for wages paid prior to 1987. An agreement, or modification of an agreement, may provide for the computation of contributions as prescribed in § 404.1256 for some employees of a political subdivision. In this situation, SSA assigns special unit numbers to the political subdivision to identify those employees. SSA does not assign a special unit number to a political subdivision in which the contributions for all employees are computed as prescribed in § 404.1256.
5. (e)Use. For wages paid prior to 1987, the employer shall show the appropriate SSA-issued identifying number, including any coverage group or payroll record unit number, on records, reports, returns, and claims to report wages, adjustments, and contributions.