All U.S. citizens must provide their valid Social Security number for inclusion on the passport. This is necessary to comply with code 26 U.S.C. 6039E, which outlines requirements for citizens.
The passport is required to show information regarding citizenship. Because of this, U.S. residents must include proof of American citizenship. This must be verified with a birth certificate, naturalization certificate or other acceptable documentation.
In addition to citizenship information, all passports must include proof of identity. This is accomplished by taking information from a driver's license, military identification or other government I.D. card.
In order to confirm identity, a photo is required to be included on all passports. This photo must be clear and in color, and 2 inches square. The photo must be recent and show the passport holders current appearance.
In addition to the basic required information, other details such as a visa stamp may be required. These requirements vary from country to country. Information on additional requirements is available from the U.S. embassy in each country.
