R.I. Gen. Laws § 45-21-18
The right to a service retirement allowance under the provisions of this chapter is vested in a member who withdraws from service prior to the attainment of the applicable minimum age of retirement as prescribed in this section, who has not received a refund; provided, that the member has completed at least ten (10) years of total service, or for members in active service on or after July 1, 2012, at least five (5) years of total service. The member becomes entitled to a service retirement allowance upon the member's attainment of the applicable minimum retirement age or at the member's option at any date subsequent to attaining that age. The rate of service retirement allowance payable in the case of any member is that provided in § 45-21-17 for the period of total service earned and accrued at the date of withdrawal from service of the member.
R.I. Gen. Laws § 45-21-18