41 CFR § 301-54.2
What is disposable pay?
June 9, 2020
Disposable pay is your compensation remaining after the deduction from your earnings of any amounts required by law to be withheld. These deductions do not include discretionary deductions such as savings bonds, charitable contributions, etc. Deductions may be made from any type of pay you receive from your agency, e.g., basic pay, special pay, retirement pay, or incentive pay.
[FTR Amdt. 92, 65 FR 21366, Apr. 21, 2000]