Section 389.21 - Payment of fees(a) Except as provided in paragraph (b) of this section, any document for which a filing fee is required by § 389.25 shall be paid for electronically at http://www.pay.gov, a secure government-wide collection portal, unless a waiver or modification of the filing fee has been requested and approved. Payments can be made directly from a bank account or by credit/debit card.(b) Registration for all air taxi operators shall be accompanied by an 8 dollar ($8) registration filing fee in the form of a check, draft, or postal money order payable to the U.S. Department of Transportation.(c) Where a document seeks authority or relief in the alternative and therefore would otherwise be subject to more than one filing fee, only the highest fee shall be required.(d) Where a document relating to a single transaction or matter seeks multiple authorities or relief and therefore would otherwise be subject to more than one filing fee, only the highest fee shall be required. Where a document relating to more than one transaction or matter seeks multiple authorities or relief, the required filing fee shall be determined by combining the highest fees for each transaction or matter. For purposes of this paragraph (d), a specific number of charters or inclusive tours described in one application will be regarded as a single transaction or matter.(e) No fee shall be returned after the document has been filed with the Department, except as provided in §§ 389.23 and 389.27 .