Whenever the goods are imported under preferential tariff treatment and supported by a proof of origin, certification of origin or certificate of origin in effect and in compliance with a treaty or a commercial agreement entered into by Mexico, and the tariff classification stated in said document differs from the tariff fraction stated in the declaration, the proof of origin, certification of origin, or certificate of origin shall be deemed valid in the following cases:

1. Whenever the proof of origin, certification or origin or certificate of origin in effect has been issued based on a tariff classification and codification system different than that used in Mexico, or in a version different to the Harmonized Commodity Description and Coding System in compliance to the amendments agreed at the World Customs Organization, as far as the amendments to the law are not carried out for this matter;
2. Whenever the Mexican customs authority has stated there is an inaccurate tariff classification of the goods;
3. Whenever the goods are imported grounded on Rule 8a. or whenever they are goods included in tariff fractions 9803.00.01 or 9803.00.02.

The previous provisions hall be applicable whenever the description of the goods referred to in the proof of origin, the certification of origin or the certificate of origin in effect corresponds to the statement in the declaration and allows the full identification of the goods filed for the clearance.

On the other hand, in compliance to the free trade treaties to which Mexico is a member, and which are in effect, goods may be imported under preferential tariff treatment and be filed for clearance along with its accessories, spare parts or tools, whenever these are classified in tariff as part of said goods. In those cases, the certification of origin or certificate or origin supporting the goods shall be valid also for the accessories, spares or tools whenever the last ones are not invoiced as separate.

Legal grounds: Article 36-A of the Customs Law and Rules 3.1.12. and 3.1.13., of the General Regulations of Foreign Trade in effect.