; or (B) provide that an employee’s compensable leave for a plan year accrue during the plan year on a proportional basis in relation to the number of compensable days provided to such employee, and except as otherwise provided in subsection (b)(4), is available to an employee as the compensable leave accrues. (4) Determining number of employees (A) In general The number of employees of an employer for a plan year shall be determined by calculating the average monthly number of employees for the preceding plan year in accordance with subparagraph (B). (B) Calculation The average monthly number of employees for a plan year shall be calculated by adding the total number of monthly employees for each month of such preceding plan year and dividing by 12. (C) Service requirement An individual shall be considered an employee for a month if such individual is an employee on at least the first day and last day of the month. (5) Years of service The determination of an employee’s years of service shall be made by the employer in a manner consistent with section 203(b)(2), except that, upon adoption of a qualified flexible workplace arrangement plan, all employees’ prior years of service with the employer maintaining the plan shall be taken into account when calculating the employee’s years of service for the purpose of this subsection. (6) Carryover An employer may permit employees to carry over unused compensable leave from one plan year to the subsequent plan year. (7) Cashout An employer may permit employees to cash out unused compensable leave after or in connection with the termination of employment. (b) Full-Time, part-Time, and new employees, and pro-Rated calculations (1) Full-time employees (A) In general For any plan year, the requirements described in subsection (a)(1) shall only apply to employees who are full-time employees. (B) Definition The employer, in its qualified flexible workplace arrangement plan, shall reasonably define full-time , when used with respect to an employee, for purposes of such plan.