If you are applying for a U.S. green card (lawful permanent residence) based on marriage, and doing so while in the U.S., through the process known as "adjustment of status," then you can expect to be called in for a personal interview. This will be held at a district office of U.S. Citizenship and Immigration Services (USCIS).
Here is some guidance on what to bring to that USCIS interview. You will also receive a list from USCIS, so read it carefully and include anything that you don't see mentioned below.
Both the immigrant and spouse will need to present valid photo identification. For the immigrant, a passport is best, though other forms of ID are acceptable. The U.S. citizen or permanent resident spouse usually presents a driver's license.
Assemble the originals of the documents you (the immigrant) used to enter the United States, and any other documents you've received from U.S. consulates or USCIS offices, such as an Advance Parole travel permit or a work permit, also called an Employment Authorization Document or EAD.
Also, if you've mailed copies of documents to USCIS, such as your marriage and birth certificates, bring the originals so the officer can review and compare them.
The U.S. spouse will need to bring the original proof of U.S. citizenship status (a birth certificate, naturalization certificate, or passport) or permanent resident status (a green card or stamp in their passport).
The USCIS officer might not ask for all of these, but you'll be glad you brought them if the officer does ask. Also realize that the officer may keep the EAD, since it's no longer valid. Your green card will serve as your proof of your right to work in the United States. It will not arrive for a few weeks, however, so if you need such proof in the meantime, perhaps to show a new employer on the first day of work, ask for either an approval letter or an I-551 stamp in your passport.
Has anything important and relevant in your life changed since filing the adjustment of status paperwork?
If, for example, you or your spouse have a new or different job, you should bring a letter from the new employer and copies of recent pay stubs. (Don't forget, your spouse's income still needs to be high enough to deal with the affidavit of support requirements. If it has gone down, you, the immigrant, might be able to help by bringing proof that you are now working in the United States.) And even if your income has not changed, prove that fact with a recent pay stub showing that the financial sponsor is still bringing in the income.
If you and your U.S. spouse have reached the two-year anniversary of your marriage since filing the application, be ready to remind the officer of this, so you'll be approved for permanent, not conditional residency.
If a tax year has passed while you waited for your interview, bring a copy of your latest tax returns (or better yet, an IRS transcript of these returns).
If the two of you are pregnant or have a new baby, bring medical records or a birth certificate to prove this; it's great evidence of a bona fide marriage.
You'll be expected to reveal bad news, too, such as if the immigrant has been arrested for or convicted of a crime. Hire an attorney if something like this has occurred.
During the course of your application process, USCIS might tell you it's okay if you haven't sent a necessary document yet because you can just bring it to the interview. For example, if you haven't already turned in the Form I-693 immigration medical examination, which must have been signed by a doctor and presented in a sealed envelope, now is the time to do so.
The interview is the most important opportunity for the USCIS officer to decide whether your marriage is bona fide, or "for real," not just a fraud to get the immigrant U.S. residence. The documents you show are important factors in this decision. They should show that you and your spouse's lives are intertwined and that you trust each other with your financial and personal matters.
Below is a list of documents most immigrants present. However, this list isn't engraved in stone. Use your imagination and be ready to do some organized "show-and-tell." No need to flood the officer with paper—copies of six items from this list would be normally be a reasonable amount, unless your case has red flags that require extra documentation to overcome.
It's not too late to hire an immigration attorney, if you're feeling at all uncertain about proving your eligibility for a marriage-based green card, or are confused by the paperwork and other requirements. The lawyer can evaluate your situation, help you sort through and prepare additional paperwork, and accompany you to the USCIS interview.