The K visa is unique. Officially it is classified as a non-immigrant visa. However, in reality it is almost like an immigrant visa, if not exactly one. This visa is for the applicant living abroad who is a fiance or fiancee engaged to marry a United States citizen.
The object of this visa is to enable its holder to gain entry into the U.S. solely to marry the U.S. citizen. If the applicant is granted a visa, he or she must enter into the marriage with the U.S.citizen within 90 days of his or her entry into the U.S., otherwise the visa will expire and the applicant fiance or fiancee must return to his or her home country. No extensions are given on a K visa, the sole exception being in cases of illness or other unforeseen emergencies. The U.S. citizen and the applicant must be able to legally marry at the time of the visa issuance, in order words if one of the parties is going through a divorce, it must be finalized before the visa can be issued. The first step towards acquiring a K-1 visa is the filing of Form I-129F (Petition for Alien Fiance(e), completed and signed by the U.S. citizen, along with supporting documents such as proof of citizenship, proof that the pair can legally wed, and items showing that a wedding will take place, such as wedding invitations or a letter from the official performing the ceremony.
In addition, satisfactory evidence establishing that both parties have previously met and known each other in person within the past two years.
This rule may be waived in the event that religious custom does not permit a prior meeting in person. The children of the applicant, if any, may be included in the same petition. Assuming that the petition is approved, the U.S.C.I.S. forwards the approved petition to the American Consulate in the foreign country in which the applicant spouse-to-be lives. The Consulate notifies the applicant that such petition has been approved and invites her or him to appear for a visa interview and to submit certain documents, such as
(a) a valid passport, birth certificate,
(b) divorce judgments if applicable
(c) a police security clearance certificate with regard to countries where the applicant lived for 6 months or more since attaining the age of 16 years
(d) Report of medical examination
(e) An Affidavit of Support must also be submitted by the petitioner along with financial documents such as tax returns and bank statements to determine his or her financial ability to support the applicant fiancee in order that the applicant will not become a "public charge" upon arrival in the U.S. Assuming that all goes well, the applicant will be issued with a K-1 visa. This visa must be used for travel within 4 months from issuance, or else a revalidation of the petition will become necessary each time the 4 month period expires.
Upon entry into the U.S. and immediately after the marriage takes place, the applicant spouse will file an adjustment of status (green card) application on Form I-485 with the USCIS, along with supporting documents.