aa. Beginning with a payroll period commencing on or after such date, as specified by a participating employer electing to contribute pursuant to the provisions of this subdivision, the contribution of each member of the retirement system in the employ of such a participating employer, whose rate of contribution is in excess of eight per centum, exclusive of any increase thereof pursuant to subdivision i of section twenty-one of this chapter or of any reduction thereof pursuant to subdivision one of section one hundred thirty-eight-b of this chapter or subdivision a of this section, shall be suspended. In the case of a participating employer any member may by written notice duly acknowledged and filed with the comptroller beginning with the payroll period commencing on or after such date as specified by a participating employer within one year after the effective date of this act or within one year after he last became a member, whichever is later, elect to waive the suspension of his contribution provided by this subdivision. One year or more after the filing thereof a member may withdraw any such waiver by written notice duly acknowledged and filed with the comptroller. Where a member makes an election to waive the suspension of his contributions as herein provided, he shall contribute to the retirement system as otherwise provided in this chapter. However, commencing with the payroll period the first day of which is nearest to July first, nineteen hundred sixty-six, the foregoing provisions of subdivision aa shall be inapplicable as to any participating employers other than those who had filed a resolution prior to the effective date of this act to participate thereunder.