Except as provided in subsections (b) and (c) of this section, on request of the Secretary, an employing unit shall provide to the Secretary a report of the separation from employment of an individual. An employing unit who submits a separation notice under this subsection shall: complete the notice on a form or in a manner that the Secretary requires; and submit the notice no later than the 8th calendar day after the day of the request. On request, an employing unit who submits a separation notice under this subsection also shall submit to the Secretary a report of the wages of any of its employees. An employing unit shall submit to the Secretary a single notice for a group of employees if the employing unit lays off at least 25 employees for the same reason at or about the same time in a single establishment for a period that is permanent, indefinite, or expected to exceed 7 days. A notice under this subsection shall: state the reason for the layoff; and list the name and Social Security number of each employee whom the layoff affects. An employing unit shall submit to the Secretary a single notice for a group of employees who become unemployed because of a labor dispute. A notice under this subsection shall: state the existence of the labor dispute without any statement about the nature of the dispute; and list the name and Social Security number of each employee whom the labor dispute affects. If the Secretary finds that the character or type of employment makes application of this section to a class of employers unreasonably onerous or impractical, the Secretary by regulation may exempt the class from the requirements of this section. An employer that fails to submit a separation notice or report of wages under subsection (a) of this section is subject to a penalty of $15 for each notice unless the Secretary waives the penalty for cause. An employer that submits a check or other negotiable instrument returned for insufficient funds in payment of any penalty under this subsection is subject to an additional penalty of $25.