OPTIONAL INCREASE IN RETIREMENT ANNUITIES.

(a) The governing body of a participating municipality by ordinance, from time to time but not more frequently than once in each 12-month period, may authorize and provide for increased annuities to be paid to retirees and beneficiaries of deceased retirees of the municipality. An annuity increased under this section replaces any annuity or increased annuity previously granted to the same person.

(b) The amount of annuity increase under this section is computed as the sum of the prior and current service annuities on the effective date of retirement of the person on whose service the annuities are based, multiplied by:

(1) the percentage change in the Consumer Price Index for All Urban Consumers, published by the Bureau of Labor Statistics of the United States Department of Labor, from December of the year immediately preceding the effective date of the person's retirement to the December that is 13 months before the effective date of the ordinance providing the increase; and

(2) 30 percent, 50 percent, or 70 percent, as specified by the governing body in the ordinance, except that if the governing body has specified a different percentage in an ordinance adopted under Section 853.404(c) and in effect on December 31, 1999, the percentage used in computing annuity increases for retirees of that municipality remains in effect until changed or discontinued under Section 853.404.

(c) Except as provided by Subsection (g), the effective date of an ordinance under this section is January 1 of the year that begins after the year in which the governing body adopts and notifies the retirement system of the ordinance.

(d) An increase in an annuity that was reduced because of an option selection is reducible in the same proportion and in the same manner that the original annuity was reduced.

(e) If a computation under Subsection (b) does not result in an increase in the amount of an annuity, the amount of the annuity may not be changed under this section.

(f) The amount by which an increase under this section exceeds all previously granted increases to an annuitant is payable as a prior service annuity, is an obligation of the municipality's account in the benefit accumulation fund, and is subject to reduction under Section 855.308(f).

(g) An ordinance under this section may not take effect until it is approved by the board of trustees as meeting the requirements of this section. The board may not approve an ordinance unless the actuary first determines that all obligations charged against the municipality's account in the benefit accumulation fund, including the obligations proposed in the ordinance, can be funded by the municipality within its maximum contribution rate and within its amortization period as in effect on the effective date of the increases.

(h) A governing body may not authorize and provide for annuity increases under this section unless it simultaneously provides for updated service credits under Subchapter E of Chapter 853.