Ill. Admin. Code tit. 80 § 1540.260
When State law requires that service credit be granted to a member during nonwork periods, such credit shall be granted based on the member's normal work schedule. Employee and employer contributions shall be payable during such non-work periods based on the member's full rate of compensation. A nonwork period is any pay period during which an employment relationship exists and throughout which the employee does no work for the employer. If such a nonwork period falls within a qualifying period, it should be considered part of that period, and the employee may make contributions at the required rate to establish service credit. Such contributions may be made without interest if paid within 6 months of the employee's return to work, or within 6 months of completing the qualifying period, whichever is later.
Ill. Admin. Code tit. 80, § 1540.260
Amended at 8 Ill. Reg. 4144, effective March 26, 1984