Ind. Code § 36-8-10-13

Sec. 13. Except as provided in section 19 of this chapter, a sheriff may participate in the pension trust in the same manner as a county police officer. In addition, a sheriff who is not participating in the pension trust after the creation of the pension trust in the sheriff's county may make a payment to the pension trust in the amount of contributions the sheriff would have made had the sheriff been participating while a sheriff, plus interest at three percent (3%) compounded annually. The sheriff is entitled to credit for the years of service as a sheriff for all purposes of the pension trust if the sheriff makes this payment.