14 C.F.R. § 262.6
Upon confirming a consumer's eligibility for a travel credit or voucher pursuant to this paragraph, a carrier must promptly issue the travel credit or voucher with a value equal to or greater than the fare (including government-imposed taxes and fees and carrier-imposed charges and prepaid ancillary service fees for services not utilized by the consumer). If a consumer has obtained a refund of the September 11th Security Fee or other government-imposed taxes and fees, then those fee amounts may be deducted from the consumer's travel credit or voucher. Nothing in this section relieves the carrier of its obligation to comply with the requirements of other Federal agencies relating to the refund of government-imposed taxes and fees.
14 C.F.R. §262.6