5 CFR § 842.907 - Withholding and contributions.
(a) During service covered under the conditions established by § 842.903 (a) or (b), the Department of Energy will deduct and withhold from the employee's base pay the amounts required under 5 U.S.C. 8422(a)(3) and submit that amount to OPM in accordance with payroll office instructions issued by OPM.
(b) During service described in paragraph (a) of this section, the employing agency must submit to OPM the Government contributions required under 5 U.S.C. 8423(a) in accordance with payroll office instructions issued by OPM.
(c) If the correct withholding and/or Government contributions are not timely submitted to OPM for any reason whatsoever, including cases in which it is finally determined that past service of a current or former employee was subject to the higher deduction and Government contribution rates, the employing agency must correct the error by submitting the correct amounts (including both employee and agency shares) to OPM as soon as possible. Even if the agency waives collection of the overpayment of pay under any waiver authority that may be available for this purpose, such as 5 U.S.C. 5584, or otherwise fails to collect the debt, the correct amount must still be submitted to OPM as soon as possible.
(d) Upon proper application from an employee, former employee or eligible survivor of a former employee, an employing agency or former employing agency will pay a refund of erroneous additional withholdings for service that is found not to have been covered service. If an individual has paid to OPM a deposit or redeposit, including the additional amount required for covered service, and the deposit is later determined to be erroneous because the service was not covered service, OPM will pay the refund, upon proper application, to the individual, without interest.
(e) The additional employee withholding and agency contributions for covered service properly made are not separately refundable, even in the event that the employee or his or her survivor does not qualify for a special annuity computation under 5 U.S.C. 8415(d).
(f) While an employee who does not hold a primary or secondary position is detailed or temporarily promoted to such a position, the additional withholdings and agency contributions will not be made.
(g) While an employee who holds a primary or secondary position is detailed or temporarily promoted to a position that is not a primary or secondary position, the additional withholdings and agency contributions will continue to be made.