41 CFR § 301-10.115
Am I authorized to receive a refund or credit for unused transportation?
June 9, 2020
No. You are not authorized to receive a refund, credit, or any other negotiable document from a carrier for unfurnished services (except as provided in §301-10.117) or any portion of an unused ticket issued in exchange for a GTR or billed to an agency's centrally billed account. However, any charges billed directly to your individually billed Government charge card should be credited to your account.
[FTR Amdt. 70, 63 FR 15955, Apr. 1, 1998; 63 FR 35537, June 30, 1998]