Look-back measurement method
(d) Look-back measurement method(1) Ongoing employees(i) In general. Under the look-back measurement method for ongoing employees, an applicable large employer determines each ongoing employee's full-time employee status by looking back at the standard measurement period. The applicable large employer member determines the months in which the standard measurement period starts and ends, provided that the determination must be made on a uniform and consistent basis for all employees in the same category (see paragraph (d)(1)(v) of this section for a list of permissible categories). For example, if an applicable large employer member chooses a standard measurement period of 12 months, the applicable large employer member could choose to make it the calendar year, a non-calendar plan year, or a different 12-month period, such as one that ends shortly before the start of the plan's annual open enrollment period. If the applicable large employer member determines that an employee was employed on average at least 30 hours of service per week during the standard measurement period, then the applicable large employer member must treat the employee as a full-time employee during a subsequent stability period, regardless of the employee's number of hours of service during the stability period, so long as he or she remains an employee.