(a) Special rule for collection of tax. Section 4264(b) provides a special rule for the collection of the tax where an unused ticket or order (or portion thereof) purchased without payment of tax is presented for refund and, as a result of the use of only a portion of the transportation purchased in connection with such ticket or order, liability for payment of tax has been incurred. In such a case, the person making the refund shall deduct the amount of the tax due, to the extent available, from the amount which would otherwise be refundable. If the redemption value of the unused ticket or order (or portion thereof) is less than the amount of the tax due on the amount paid for the travel actually performed, the person redeeming the unused ticket or order (or portion thereof) shall make no refund but shall apply the entire amount against the tax due and shall collect any additional tax due or, within 90 days, shall make a report of the amount of the tax remaining uncollected, together with the name and address of the person who sought the refund. The report shall be made to the office of the district director of internal revenue for the district in which the person making such report is located, and a copy of the report shall be furnished to the person presenting the unused ticket or order for redemption.

(b) Return of tax. Any person who has made a collection of tax in accordance with the preceding paragraph shall include such amount in his regular return of taxes required to be collected under section 4291.

(c) Illustration. A carrier receives for redemption a ticket purchased in the United States for transportation from Calgary, Canada, to Edmonton, Canada, which the purchaser bought for use in conjunction with a ticket for nonstop transportation from Seattle to Calgary. The person applying for the refund does not establish to the satisfaction of the carrier that the tax on the Seattle-Calgary ticket has been paid or that the Seattle-Calgary ticket has been redeemed. The carrier, before making any refund for the unused ticket, is required to deduct from the amount otherwise refundable the tax applicable to the amount paid by the purchaser for the transportation from Seattle to Calgary and to report the tax so collected in its quarterly return of Form 720. In the event that the redemption value of the unused Calgary to Edmonton ticket is less than the amount of the tax due on the amount paid for the transportation from Seattle to Calgary, the carrier should not make any refund but should apply against the outstanding tax the entire amount refundable and should either collect the balance of the tax due or make a report, within 90 days, to the office of the district director of internal revenue for the district in which the carrier is located, setting forth the name and address of the person seeking the refund and the amount of the tax remaining uncollected.