Large employer means, in connection with a group health plan with respect to a calendar year and a plan year, an employer who employed an average of at least 51 employees on business days during the preceding calendar year and who employs at least 1 employee on the first day of the plan year. A State may elect to define large employer by substituting 101 employees for 51 employees. In the case of an employer that was not in existence throughout the preceding calendar year, the determination of whether the employer is a large employer is based on the average number of employees that it is reasonably expected the employer will employ on business days in the current calendar year.
45 CFR § 144.103
For purposes of parts 146 (group market), 147 (group and individual market), 148 (individual market), and 150 of this subchapter, the following definitions apply unless otherwise provided: