FMSCA Regulation 377.209
377.209 Additional charges.
When a carrier
(a) Has collected the amount of tariff charges represented in a freight bill presented by it as the total amount of such charges, and
(b) Thereafter presents to the shipper another freight bill for additional chargesthe carrier may extend credit in the amount of such additional charges for a period of 30 calendar days from the date of the presentation of the freight bill for the additional charges.
