(a) A member is eligible to retire and receive a full service retirement annuity with full benefits from the pension system when the member has at least 15 years of qualified service credited in the pension system and has attained the age of 55.     
      (b) A member is eligible to retire and receive a partial service retirement annuity from the pension system when the member has at least 10 years of qualified service credited in the pension system and has attained the age of 55. Such partial retirement benefit shall accrue and be calculated as a percentage of a full service retirement benefit determined in §308.2(f) of this title (relating to Service Retirement Annuity) at the following rates:      
        (1) 50 percent after the first 10 years of credited qualified service; and       
        (2) An additional 10 percent a year for the next five years of credited qualified service.       
      (c) Vested retirement benefits, including accrued partial service retirement benefits, are nonforfeitable. A retirement benefit also becomes nonforfeitable when a member attains normal retirement age or, to the extent funded, on the termination or partial termination of the pension system or the complete discontinuance of contributions to the pension system. A person whose retirement benefit met a partial vesting requirement as it existed on December 31, 2006, is eligible to retain that eligibility and the base amount of that benefit as it existed on that date.     
     Source Note:        The provisions of this §308.1 adopted to be effective October 2, 2005, 30 TexReg 6062; amended to be effective July 26, 2006, 31 TexReg 5810; amended to be effective October 18, 2015, 40 TexReg 7103; amended to be effective December 31, 2019, 44 TexReg 8333