CMS Pub. 100-05, ch. 2, § 10.3

The working aged MSP provision applies only to GHPs of employers with 20 or more

employees and to multi-employer and multiple employer GHPs in which at least one

employer employs 20 or more employees. See 42 CFR § 411.100(a)(1)(i). 42 CFR §

411.170(a)(2)(i) which specifies this requirement is met if an employer has 20 or more

full-time and/or part-time employees for each working day in each of 20 or more

calendar weeks in the current or preceding year. An employer is considered to have

20 or more employees for each working day of a particular week if the employer has

at least 20 full-time or part-time employees on its employment rolls each working day

of that week. This condition is met as long as the total number of individuals on the

employer's rolls adds up to at least 20 regardless of the number of employees who

work or who are expected to report for work on a particular day. Self-employed

individuals participating in a GHP are not counted as employees for purposes of

determining if the 20-or-more employee requirement is met. An individual is

considered to be on the employment rolls even if the employee does not work on a

particular day. An employer may not have different employment rolls for different

days reflecting those scheduled.

Where an employer does not have 20 or more employees in the preceding year, it is

required to offer its employees and spouses age 65 or over primary coverage beginning

with the point in time at which the employer had 20 or more employees on each

working day of 20 calendar weeks of the current year. The employer is then required to

offer primary coverage for the remainder of that year and throughout the following year

even if the number of employees drops below 20 after the employer has met the

requirement.

The 20-or-more employees requirement must be met at the time the individual receives

the services for which Medicare benefits are claimed. During the time the employer has

met the 20-or- more employees requirement in the current year or in the preceding

calendar year, the GHP is primary payer. An employer that meets this requirement must

provide primary coverage even if less than 20 employees participate in the GHP.