Most immigrants applying for a family-based U.S. green card (lawful permanent residence) must, as part of the application process, have their petitioner (the U.S. citizen or permanent resident who filed their I-130 visa petition) fill out and submit an Affidavit of Support on Form I-864. (This form is prepared by U.S. Citizenship and Immigration Services (USCIS), and available on the I-864 page of its website.)
The purpose of the Affidavit of Support is to assure the U.S. government that the immigrant is not inadmissible as someone likely to become a public charge--that is, receive need-based government assistance (often called "welfare"). The Affidavit represents the petitioner/sponsor's promise to support the immigrant financially for a period of years, so that he or she will not need such assistance -- or at least to pay back (reimburse) any government agencies from which the immigrant does claim such assistance.
However, a few applicants are exempt from the Affidavit of Support requirement, and do not need to submit a Form I-864 at all. We'll review those here.
Immigrants who are exempt include those who have either:
The concept is that a financial sponsor’s responsibility lasts until the immigrant has (among other possibilities) earned 40 work quarters credited toward Social Security. (A work quarter is approximately three months, but it depends partly on how high your earnings and the minimum for the year in question.) So if you have already reached the 40 quarters on your own, through lawful employment--perhaps while in the U.S. as a student or H-1B worker--there is no need for the sponsor to fill out an Affidavit of Support for you.
And, in an interesting twist, the immigrant can be credited for work done by his or her U.S. spouse during their marriage, or by a U.S. parent while the immigrant was under the age of 18.
Under the Child Citizenship Act (CCA), certain immigrant children will become U.S. citizens automatically, as soon as they become U.S. permanent residents. This is called "derivation" of citizenship. Such applicants do not need an I-864 Affidavit of Support to be filed for them. There is no need to file documentary proof of eligibility under this category.
Widows and widowers of U.S. citizens may, regardless of the duration of their marriage, self-petition for or continue with their application for U.S. residence, so long as they do so within the two years of the U.S. citizen's death and do not remarry. They will not need to submit an I-864 Affidavit of Support.
Their approved Form I-360 will be sufficient proof of their exemption. If the deceased U.S. citizen filed an I-130 visa petition before the death, it converts to an I-360 automatically, though the immigrant will need to advise USCIS of the death first.
Abused or battered spouses or children self-petitioning for U.S. green card under the Violence Against Women Act (VAWA) are also exempt from the I-864 Affidavit of Support requirement.
Their approved Form I-360 will be sufficient proof of their exemption.
You cannot just leave Form I-864 out of your application packet and expect the immigration authorities to figure out the reason. You will instead need to include a form called an I-864W, explaining the grounds for the exemption.
For help with filling it out based on work history, see Preparing Form I-864W Affidavit of Support Exemption Form Based on 40 Quarters Worked. And, if claiming the work-based exemption, you will have to prove how many quarters of work your spouse or you has done. Contact Social Security about getting a certified statement with this information.