19 CFR § 10.599 - Fungible goods and materials.

(a) General. A person claiming that a fungible good or material is an originating good may base the claim either on the physical segregation of the fungible good or material or by using an inventory management method with respect to the fungible good or material. For purposes of this section, the term “inventory management method” means:

(1) Averaging;

(2) “Last-in, first-out;”

(3) “First-in, first-out;” or

(4) Any other method that is recognized in the Generally Accepted Accounting Principles of the Party in which the production is performed or otherwise accepted by that country.

(b) Duration of use. A person selecting an inventory management method under paragraph (a) of this section for a particular fungible good or material must continue to use that method for that fungible good or material throughout the fiscal year of that person.