5 U.S. Code § 5407
5.U.S. Code § 5407 is about Nature of payment. It is under Part 3 (Employees) Subpart D (Pay and Allowances) Chapter 54 (Human Capital Performance Fund) of Title 5 (Government Organizations and Employees) of the Code.
Any payment to an employee under this section shall be part of the employee’s basic pay for the purposes of subchapter III of chapter 83, and chapters 84 and 87, and for such other purposes (other than chapter 75) as the Office shall determine by regulation.