(a) Upon a member's retirement, as provided in this article, he or she shall receive a straight life annuity equal to one and five-tenths percent of his or her final average salary multiplied by the number of years, and fraction of a year, of his or her credited service in force at the time of his or her retirement, subject to reduction if necessary to comply with the maximum benefit provisions of Section 415 of the Internal Revenue Code and section twenty-seven-a of this article: Provided, That the final average salary used in this calculation does not include any lump sum payment for unused, accrued leave of any kind or character. The credited service used for this calculation may not include any period of limited credited service: Provided, however, That after March 1, 1970, all members retired and all members retiring shall receive a straight life annuity equal to two percent of his or her final average salary multiplied by the number of years, and fraction of a year, of his or her credited service, exclusive of limited credited service in force at the time of his or her retirement, subject to reduction if necessary to comply with the maximum benefit provisions of Section 415 of the Internal Revenue Code and section twenty-seven-a of this article. In either event, upon his or her retirement he or she has the right to elect an option provided in section twenty-four of this article. All annuity payments shall commence effective the first day of the month following the month in which a member retires or a member dies leaving a beneficiary entitled to benefits and shall continue to the end of the month in which the retirant or beneficiary dies, and the annuity payments may not be prorated for any portion of a month in which a member retires or retirant or beneficiary dies. Any member receiving an annuity based in part upon limited credited service is not eligible for the supplements provided in sections twenty-two-a through twenty-two-d, inclusive, of this article.

(b) The annuity of any member of the Legislature who participates in the retirement system as a member of the Legislature and who retires under this article or of any former member of the Legislature who has retired under this article (including any former member of the Legislature who has retired under this article and whose annuity was readjusted as of March 1, 1970, under the former provisions of this section) shall be increased from time to time during the period of his or her retirement when and if the legislative compensation paid under section two, article two-a, chapter four of this code, to a member of the Legislature shall be increased to the point where a higher annuity would be payable to the retirant if he or she were retiring as of the effective date of the latest increase in legislative compensation, but on the basis of his or her years of credited service to the date of his or her actual retirement.