If any change or error results in an employee or beneficiary receiving from the retirement system more or less than he would have been entitled to receive, then on discovery of the error, the retirement system shall correct it and, so far as practicable, adjust the payments in such a manner that the actuarial equivalent of the benefit to which he was correctly entitled shall be paid.
The application of any member for prior service credit or credit for all previous service shall be approved if the employer, for whom the service was rendered stipulates, in writing, to the retirement system that the information necessary for the award of such credit was not presented to the employee and agrees to make the necessary additional contribution to the contingent reserve fund and the employee makes the required contributions, if any.