20 CFR § 209.13 - Employers' gross earnings reports.
(a) Each employer is required to report the gross earnings of a one-percent sample group of railroad employees. The gross earnings sample is based on the earnings of employees whose social security numbers end with the digits 30. This report is used to determine:
(1) Tax and benefit amounts involved in the Financial Interchange with the Social Security Administration and the Health Care Financing Administration; and
(2) Estimated tax income accruing to the railroad retirement system in future periods.
(b)Employers shall submit reports annually for employees in the gross earnings sample. Such reports shall include the employee's gross annual earnings, which includes all compensation taxable under the hospital insurance portion of the tier I tax rate. Employers with 5,000 or more employees shall provide a monthly or quarterly breakdown of the year's earnings. Employers with fewer than 5,000 employees may submit an annual amount only, although a monthly or quarterly breakdown is preferable. Gross earnings are to be counted for the same time period as used in determining the employer's annual report of creditable compensation. The reports are to be prepared in accordance with prescribed instructions and filed in accordance with § 209.4 of this part.