The calculation of average salary for retirement purposes shall allow the use of the salary earned during any twenty-four (24) consecutive months producing the highest such average; not counting any month in which the member normally would be under contract but for which no contributions were reported, provided that additional months would be used only if the member did not have credit for two (2) full years of service for the twenty-four (24) month period.
Ga. Comp. R. & Regs. R. 513-5-1-.08
O.C.G.A. Secs. 47-3-26, 47-3-120.