The form is required for a Freedom of Information Act (FOIA) or Privacy Act Request or Amendment of Record under the Privacy Act. Form G-639 requires the name, address and telephone of the individual making the request. If the subject of the request for information is deceased, proof of death must be attached to Form G-639. If the person for whom the information being sought is not the same as the requester, the person who is the subject of the request must also sign Form G-639 to consent to the release of information. Form G-639 allows the subject of the release of information to select all or a portion of the records for release. He or she must indicate in section 3 of Form G-639 what portion of the record information is subject to the consent for release of information and identify the specific documents, records or information sought. The applicant may identify the purpose for which the information is being sought.

Form G-639 requires the following data for the subject of record: Other names used, name at the time of entry into the United States, I-94 Admission Number, Alien Registration Number, Petition or Claim Receipt Number, County of Birth, and Date of Birth. Information as to other family members is also required for Form G-639 including the family member's full name, relationship to person subject to the release of information, father's name, mother's name, county of origin, Port of entry into the United States, Date of Entry, Manner of Entry and Mode of Travel.

Form G-639 requires verification of the Subject of Record's Identity either by in-person identification, notarized Affidavit of Identity, or other reliable form of identification. An original notarized signature is required for Form G-639, whether or not the document is signed in United States.