(a) Prior service credit may be obtained by a clerk or register in office on October 1, 1976, for years served in the individual capacity of clerk or register on a continuous basis. Prior service credit must either be for time served as clerk or as register without allowance for service as both clerk and register; provided, that prior service credit for each individual position may not be combined. A person seeking to qualify as supernumerary clerk shall count only time served as clerk, and one seeking to qualify as supernumerary register shall count only time served as register. Prior service credit may also be obtained by a clerk or register for any years served in the capacity of probate judge, provided such service as probate judge was continuous. If any person subject to the provisions of this division shall seek to obtain prior service as either clerk or register, he shall contribute to the Clerks' and Registers' Supernumerary Fund, State of Alabama, for each year for which prior service credit is sought up to a maximum of 15 years. No official under this division shall be eligible for prior service credit to become supernumerary unless payments as provided hereinafter have been paid. However, any official who otherwise qualifies may become eligible upon October 1, 1978, or within two years thereof, by paying in a lump sum computed on the basis of the formula enumerated in this section or by paying such sum into the appropriate fund, in equal installments, with no interest, over a two-year period from October 1, 1978; provided, that no compensation benefits shall accrue to any official electing to become supernumerary hereunder until all contributions have been paid.

(b) Payments necessary for prior service credit shall be computed as follows:

(1) Circuit clerks shall contribute an amount equal to five percent of their salary or, if on fees, the base sum payable by the state as salary to circuit clerks pursuant to Section 12-17-92, for each year for which prior service credit is sought; and

(2) Circuit registers shall contribute an amount equal to five percent of the highest net annual income received for services rendered for any one year of the three years next preceding February 14, 1975.