When do I need to fill out an Affidavit of Support?

Immmigrants who are applying to obtain a Green Card through a family member must submit an I-864, Affidavit of Support form. The Affidavit of Support form is used to show the USCIS that a Green Card applicant has a financial sponsor and has enough financial support to live without concern of becoming dependant on U.S. government welfare.

Form I-864 is legally required for many family-based and some employment based immigrants to show that, when they plan to immigrate to the US, they have adequate means of support. Generally, the following immigrants need an Affidavit of Support namely:
1)Family based immigrant visa applicants, including certain orphans, and
2)Employment based immigrant visa applicants whose relative filed the visa petition or has at least 5 percent or more ownership interest in the business that filed the petition.
So who qualifies as a sponsor in the I-864, affidavit of support case?

A sponsor must be at least 18 years old and either an American citizen or a lawful permanent resident (LPR). The sponsor should also have a domicile (residence) in the United States. The petitioner who is residing abroad should have a principal residence in the U.S. and intend to maintain that residence in the future. Lawful permanent resident sponsors should show they are maintaining their permanent resident status.

Many U.S. citizens and permanent residents reside outside the United States on a temporary basis, usually for work or due to family situations. This "Temporary" status will cover an extended period of residence abroad. Certain conditions need to be fulfilled by the sponsor living abroad to be considered domiciled in the United States.
An American citizen or permanent resident spouse or his /her dependent who has maintained a residence in the U.S. and/or whose spouse/parent works would also qualify as a sponsor related to the I-864, Affidavit of Support form.

Often, applicants get confused with the Form I-864 and Form I-134. The I-134 (affidavit of support) is not a legally binding affidavit, it is used for nonimmigrant visas. Until you marry (and subsequently file for Adjustment of status), the non US Citizen fiancé(e) will hold a non immigrant visa. This allows them to get into the US before having a legal relationship with the US Citizen fiancé(e).

Whereas the I-864 (Affidavit of Support) is a legally binding contract proving that the sponsor will be financially responsible for the immigrant in the event the immigrant attempts to benefit from certain federal aid programs. This form is filed at the Adjustment of Status part of the journey (after the Non US Citizen has traveled to the States and got married). This form is several pages long, demands detailed financial information, and is legally binding.

Although USCIS does not charge a fee for this I-864 form, a $70 fee is charged by the Department of State when the Affidavit of Support form is reviewed domestically. Whereas it does not apply when the Affidavit of Support is filed abroad.

The National Visa Center processes the immigrant visa petitions after the USCIS approves them. A bill will be sent to the petitioner by the National Visa Center asking him/her topay an AoS processing fee when the immigrant visa case is current or about to become current, Instructions on where and how to pay the bill will be sent along with the bill.