Maquiladoras are Mexican corporations that assemble imported components for export to other countries. Maquilas or Twin-Plants have special privileges that make them attractive to an offshore manufacturer, some of them are: duty reduction incentives, temporary import of raw materials and equipment without duty and simplified customs procedures among others.

There are three common business structures for manufacturing in Mexico under a Maquila program: Wholly-Owned Subsidiary, Shelter Program and Contract Manufacturing.

Ordinarily, all of a maquiladora's products are exported, either directly, or indirectly, through sale to another maquiladora or exporter. The type of production may be the simple assembly of temporarily imported parts; the manufacture from start to finish of a product using materials from various countries, including Mexico; or any conceivable combination of the various phases involved in manufacturing, or even non-industrial operations, such as data-processing, packaging, and sorting coupons.

Any product can be manufactured or assembled, packaged, processed, sorted, produced in whole or in part, transformed, rebuilt. What to produce in a maquiladora is dependent on the parent company's business considerations, including available markets and duties assessed on imports into those markets.

One consideration often overlooked by companies setting up maquiladora operations is U.S. Customs. There are several benefits available relating to U.S. duties, depending on components and/or type of product the maquiladora is producing. There are harmonized tariff sections 9802.00.60 and 9802.00.40, where duty is assessed only on value added, and there is the United States Generalized System of Preferences, where if 35% or more of the product is deemed Mexican content, it may enter duty free. Before an operation gets underway, any necessary U.S. Customs rulings should be obtained to assure the benefits expected regarding duties.

In general terms a Maquiladora Plant, may import in bond whatever is needed directly or indirectly to support the production process. This includes line machinery and equipment, raw materials and parts, item for safety and health, boxes, labels, manuals and pamphlets, anti-pollution equipment, and equipment necessary for administration, tools and spare parts. As of the December 1989 Maquiladora Decree, computers and telecommunications equipment are included among the items that can be brought in as temporary imports.

Installed equipment and machinery, and the various types of equipment used to monitor production and attend to administration may remain in Mexico as long as the Maquila Program continues. Materials and parts consumed in the production process, and shipping-related items, are permitted to remain in Mexico for six months, an extension being available as long as the total period does not extend beyond one year. Trailers and trailer parts may remain only three months.

Maquiladoras are permitted to bring whatever professional or personnel for positions of trust they need to serve as managers, technicians and in other fields requiring specialization. These foreigners may bring their families with them. However, foreigners must obtain the proper visas from the General Bureau of Immigration Services. Ordinarily, the visas are non-immigrant visas known as FM-3's, good for one year and yearly renewable.