(a) Each retirement annuity payable under this subtitle consists of a prior service annuity and a current service annuity.
(b) A prior service annuity is actuarially determined from any updated service credit or any prior service, special prior service, or antecedent service credit in effect for a member on the date of retirement, plus accumulated interest.
(c) A current service annuity is actuarially determined on the date of a member's retirement from the sum of:
(1) the amount credited to the member's individual account; and
(2) an additional amount from the benefit accumulation fund equal to the amount in the member's individual account or a greater amount authorized by a participating municipality under Section 855.501.
(d) Notwithstanding any other provision of this subtitle, instead of an annuity, a person will receive from the retirement system a single payment equal to the sum of the following if on the date of that person's retirement that sum is $10,000 or less:
(1) any updated service credit or any prior service, special prior service, or antecedent service credit for that person on the date of retirement, plus accumulated interest;
(2) the amount credited to the person's individual account; and
(3) an additional amount from the benefit accumulation fund equal to the amount in the member's individual account or a greater amount authorized by a participating municipality under Section 855.501.