If you became a U.S. conditional resident based on marriage to a U.S. citizen, and you filed Form I-751 (to remove the conditional nature of your permanent residence) with U.S. Citizenship and Immigration Services (USCIS) during the 90-day period before your status would expire, your status will be extended for a period of months. That's to give USCIS time in which to review the I-751 and decide whether to grant you a permanent green card.
However, it's possible that USCIS won't answer your petition before those months are over and your green card does, in fact, expire. What then?
This is where the receipt notice you hopefully got from USCIS becomes important.
Once the USCIS Service Center has received your I-751 application is and reviewed it to see that you included all the appropriate documents and fee, you will get a receipt notice on USCIS Form I-797. Several weeks may pass before you get this receipt notice.
The I-797 receipt notice is an important document. It extends your residency for a period designated by USCIS (normally 18 months, though during the pandemic it's been lengthened to 48 months owing to agency processing delays).
The notice will be your only proof of your legal status after you green card expires. The notice is a bit awkward to show to employers, border patrol officers, and others, but it really is an official document.
You must, however, also carry your expired green card with you at the same time. That's because your card, unlike the receipt, has your photo on it.
You will, during this time period (between filing Form I-751 and USCIS approval for permanent residence), be sent an appointment notice stating when and where you must appear for biometrics. This is usually done at a USCIS Application Support Center (ASC). Biometric processing includes taking your photograph, signature, and index fingerprint, for use in generating your new green card. If you are between ages 14 and 79, it also includes taking your fingerprints, in order to do another criminal background check.
Most people receive their permanent resident cards before the expiration of their extension on Form I-797. If you don't, however, do not worry that this will affect your legal status in the United States. You will remain a conditional resident until USCIS makes a decision on your application.
If, however, you need evidence of your legal status during this limbo period, get in touch with the USCIS Contact Center. The officer there should double check that your case is still pending. If need be, the officer can make an appointment for you at a local USCIS office. There, USCIS can give you what's called an I-551 stamp in your passport, which will serve as evidence of your status (with an expiration date).
If you request it, the USCIS information officer will also send an inquiry to the Service Center handling your case, pointing out that your case has gone beyond normal processing time.
With any luck, the USCIS Service Center will approve your permanent residence by mail before long. Or, it may call you and your spouse in for an interview first.
If it's getting close to the time when you can apply for U.S. citizenship and USCIS still has not given you a decision on your I-751, you don't have to wait to apply for citizenship.
Although USCIS cannot actually give you citizenship unless the I-751 is approved, if it sees that you still have an I-751 pending when you apply, it will take care of your I-751 first, then process your citizenship application.
Do not travel with an expired receipt notice! If you do not get your permanent resident card by the time your receipt notice expires, you'll need to get a temporary stamp in your passport before leaving the United States. If you fail to do so, you might not be let back in.