To purchase a firearm in the United States, potential buyers must fill out a Bureau of Alcohol, Tobacco, Firearms and Explosive's Firearms Transaction Form.
The form asks for the buyer's name, address, date of birth, Social Security number and identifying features, such as height, weight and ethnicity. The form also asks if potential buyer has ever been convicted of a felony, renounced his or her citizenship, abuse drugs, been dishorably discharged from the military or convicted of domestic battery. It also asks if the person has ever been deemed as "mentally defective" by a court or board, been committed to a mental institution or in the United States as an illegal alien.
The six-page form also asks several questions of the firearm seller.
To view or download the form, go to http://www.atf.gov/forms/download/atf-f-4473-1.pdf