5 U.S.C. § 5551 Lump-sum payment for accumulated and accrued leave on separation
(a) An employee as defined by section 2105 of this title or an individual employed by the government of the District of Columbia, who is separated from the service, is transferred to a position described under section 6301(2)(B)(xiii) of this title, or elects to receive a lump-sum payment for leave under section 5552 of this title, is entitled to receive a lump-sum payment for accumulated and current accrued annual or vacation leave to which he is entitled by statute. The lump-sum payment shall equal the pay (excluding any differential under section 5925 and any allowance under section 5928) the employee or individual would have received had he remained in the service until expiration of the period of the annual or vacation leave. The lump-sum payment is considered pay for taxation purposes only. The period of leave used for calculating the lump-sum payment shall not be extended due to any holiday occurring after separation. For the purposes of this subsection, movement to employment described in section 2105(c) shall not be deemed separation from the service in the case of an employee whose annual leave is transferred under section 6308(b).
(b) The accumulated and current accrued annual leave to which an officer excepted from subchapter I of chapter 63 of this title by section 6301(2)(x)–(xiii) of this title, is entitled immediately before the date he is excepted under that section shall be liquidated by a lump-sum payment in accordance with subsection (a) of this section or subchapter VIII of this chapter, except that the payment is based on the rate of pay which he was receiving immediately before the date on which section 6301(2)(x)–(xiii) of this title became applicable to him.
(c)(1) Annual leave that is restored to an employee of the Department of Defense under section 6304(d) of this title by reason of the operation of paragraph (3) of such section and remains unused upon the transfer of the employee to a position described in paragraph (2) shall be liquidated by payment of a lump-sum for such leave to the employee upon the transfer. (2) A position referred to in paragraph (1) is a position in a department or agency of the Federal Government outside the Department of Defense or a Department of Defense position that is not located at a Department of Defense installation being closed or realigned as described in section 6304(d)(3) of this title.