(a) Presentation of freight bills by mail. When carriers present freight bills by mail, the time of mailing shall be deemed to be the time of presentation of the bills. The term freight bills, as used in this paragraph, includes both paper documents and billing by use of electronic media such as computer tapes or disks, when the mails are used to transmit them.

(b) Payment by mail. Wnen shippers mail acceptable checks, drafts, or money orders in payment of freight charges, the act of mailing them within the credit period shall be deemed to be the collection of the tariff charges within the credit period for the purposes of the regulations in this part.

(c) Disputes as to date of mailing. In case of dispute as to the date of mailing, the postmark shall be accepted as such date.