29 CFR 1450.23 - Deduction from pay.
(1) Ordinarily, debts to the United States should be collected in full, in one lump-sum. This will be done when funds are available. However, if funds are unavailable for payment in one lump sum, or if the amount of the debt exceeds 15 percent of disposable pay for an officially established pay interval, collection will normally be made in installments.
(3) Deduction will generally commence with the next full pay interval (ordinarily the next biweekly pay period) following written consent by the employee to salary offset, waiver of hearing, or the decision issued by the hearing officer.
(4) Installment deductions must be made over a period not greater than the anticipated period of employment except as provided in § 1450.24.