26 U.S.C. § 6039D: Returns and records with respect to certain fringe benefit plans

the number of employees of the employer, the number of employees of the employer eligible to participate under the plan, the number of employees participating under the plan, the total cost of the plan during the year, the name, address, and taxpayer identification number of the employer and the type of business in which the employer is engaged, and the number of highly compensated employees among the employees described in paragraphs (1), (2), and (3). Each employer maintaining a specified fringe benefit plan during any year shall keep such records as may be necessary for purposes of determining whether the requirements of the applicable exclusion are met. who maintains a specified fringe benefit plan during any year for which a return is required under subsection (a), and who is required by the Secretary to file an additional return for such year, The term “specified fringe benefit plan” means any plan under section 79, 105, 106, 125, 127, 129, or 137. The term “applicable exclusion” means, with respect to any specified fringe benefit plan, the section specified under paragraph (1) under which benefits under such plan are excludable from gross income. In the case of a multiemployer plan, the plan shall be required to provide any information required by this section which the Secretary determines, on the basis of the agreement between the plan and employer, is held by the plan (and not the employer).