Determine if you are eligible to sponsor the immigrant by referring to USCIS Form I-864P, Poverty Guidelines. If your income fails to meet these guidelines, you can still sponsor the immigrant jointly with a relative (a spouse, adult child, parent or sibling) who is also a household member, or someone you claimed as a dependent on your most recent tax return, as long as your combined income meets the guidelines. In this case, you will have to file Form I-864A as well as Form I-864. If you sponsored the immigrant's immigration application, you must either sponsor or co-sponsor the immigrant.
Download and complete IRS Form 4506-T and send it to the IRS, or call the IRS at 1 (800) 829-1040 and ask the representative to issue you a transcript of your most recent income tax return. It should be issued to you in about two weeks. You cannot submit your own copy. You will also need your W-2s/1099s (whichever is applicable).
Assemble documentary evidence of your current employment and income (preferably a signed letter from your employer on company letterhead, plus pay stubs or bank transfer statements).
Assemble evidence of your assets, including bank statements and stock certificates. The more liquid these assets are, the more weight they will carry in the determination of whether you qualify to sponsor the immigrant.
Complete Form I-864 (and Form I-864A if necessary) and have the immigrant include it with (i) the visa application packet to be filed with a U.S. embassy or consulate, if the immigrant is overseas; or (ii) the immigrant's Form I-485, Application to Register Permanent Residence or Adjust Status, if the immigrant is already in the United States. All of your financial documentation should be included.
Promptly file USCIS Form I-865 with the USCIS every time you change your address, until your obligation under Form I-864 expires. Your sponsorship obligation will expire as soon as the immigrant becomes a U.S. citizen or has worked in the United States for 10 years, whichever happens first.