Section 831.404 - Procedure for making voluntary contributions(a) To make voluntary contributions to the Civil Service Retirement and Disability Fund, an eligible individual must first apply on a form prescribed by OPM. OPM will establish a voluntary contribution account for each eligible individual who elects to make voluntary contributions and notify the individual that a voluntary contribution account has been established. An eligible individual may not make voluntary contributions until notified by OPM that an account has been so established.(b) After receiving notice from OPM under paragraph (a) of this section, an eligible individual may forward voluntary contributions to the Office of Personnel Management, at the address designated for that purpose. Voluntary contributions must be in the amount of $25 or multiples thereof, by money order, draft, or check payable to OPM.(c) The total voluntary contributions made by an employee or Member may not exceed, as of the date any contribution is received, 10 percent of the aggregate basic pay received by the eligible individual.(1) Employees are responsible for not exceeding the 10 percent limit.(2) When the employee retires or withdraws the voluntary contributions, OPM will check to determine whether the 10 percent limit has been exceeded.(3) If the total of voluntary contributions received from the employee exceeds the 10 percent limit, OPM will refund without interest any amount that exceeds the 10 percent limit.