It is important to know that any imported vehicle , new or used, must comply with U.S. safety, fuel savings, and air pollution control standards. If an imported vehicle does not conform to these standards, it must be brought into conformity; otherwise it must be destroyed or exported. Both the Department of Transportation (DOT) and the Environmental Protection Agency (EPA) advise that, although a nonconforming car may be conditionally admitted, modifications may be impractical, impossible or require such extensive engineering that the labor and material cost may be prohibitive.
Foreign automakers can also certify whether or not an automobile conforms to U.S. standards. 

Cars that are more than 25 years old are exempt from EPA and DOT requirements.
In 2005, model year 1980 and older cars are exempt.

The importer must be able to demonstrate to U.S. Customs that the vehicle model is either a U.S. version or that it conforms to EPA and DOT requirements in order to obtain Customs clearance. Valid proof of ownership, which is an original certificate of title, or a certified copy of the original must be also be presented to Customs. A U.S. version vehicle is manufactured with a label in the engine compartment that states, in the English language, the vehicle conforms to all U.S. Environmental Protection Agency regulations. If this label is not present, the importer will have to obtain a letter from the manufacturer stating that the vehicle conforms to EPA standards.

Vehicles manufactured to meet DOT FMVSS regulations will have a certification label affixed by the original manufacturer in the area of the driver-side door. If this label is not on the car, a manufacturer's letter will be required as proof that the car conforms to DOT safety requirements. If you are unable to demonstrate that the vehicle conforms to U.S. safety and emission requirements, you will have to import it through a registered importer. This can be very expensive, as the car will have to be reconfigured so as to be brought into compliance.

To import a (compliant)vehicle, an entry must be filed with Customs. To do this, you should declare the vehicle to a Customs inspector when it first arrives in the U.S.(assuming you are driving the car through a land border) At that time, you will also need to present a completed EPA Form 3520-1 and DOT form HS-7 and the manufacturer's letter if necessary. You will receive the entry summary document CF 7501 from Customs. This form is needed to register the car in your state of residence. The importer is required to pay 2.5% duty, which is assessed based on the purchase price or blue book value. Customs may seize a non U.S. version vehicle falsely declared as a U.S. version. Personal importations of vehicles usually do not require a Customs bond. However, the Customs inspector has the authority to require a Customs bond.

Vehicles imported for resale must have a Customs bond. You can obtain a Customs bond from a surety company. A list of sureties is available on the Treasury web site at www.fms.treas.gov , under publications, circular 570. (If you are having the car shipped, we advise making arrangements with a Customs broker to clear your car through Customs on your behalf.) For additional information on how to bring a car or car parts into the U.S. for personal use, please reference our brochure "Importing or Exporting a Vehicle." If you intend to import cars and car parts for resale, you should read our publication entitled "Importing Into the United States."

It is illegal to sell a non-compliant vehcile in the U.S. If you have imported, bought or been given a noncompliant vehicle, it must either be converted by a registered importer or exported. If you purchase a vehicle imported into the U.S. by someone else, and that vehicle turns out to be noncompliant, Customs can seize the car. Buyers should always make sure that a car is legally registered in the U.S. before they purchase it to avoid this situation.

Additional information on importing an automobile can be found on the U.S. Customs website under Publications, Videos and Forms in the Importing and Exporting section and on the DOT website and on the EPA website.