If you received a "conditional" or two-year green card after marrying a U.S. citizen, you probably know that your path toward full, permanent U.S. residence still contains more steps. You will need to file a petition with U.S. Citizenship and Immigration Services (USCIS) to remove the "conditions" on your U.S. residency. (See Marriage-Based Conditional Residents: When and How to Apply for a Permanent Green Card). In most cases, the petition must be filed by the immigrant and the spouse together, and submitted within the 90 days before the immigrant's two years as a conditional resident are over.
But what if your husband or wife has died at some point during those two years or soon after, before you submitted or received a decision on your I-751 petition?
If your spouse signed the petition (the "I-751") to remove conditions on residence and died before you could file it, you should not send that I-751, but rather file a different one with just your signature, asking for a "waiver" of the requirement that both spouses sign the petition. (See 8 C.F.R. § 216.5.)
Where the form asks for, "Basis for Petition," skip the "Joint Filing" boxes and go to the "Waiver or Individual Filing Request" section, then request the waiver by checking the box saying, "My spouse is deceased." Include a copy of the death certificate.
You will still need to submit all the evidence that shows that your marriage was "bona fide" (real) along with your I-751.
If your spouse died after you filed an I-751, and it contained both your signatures, USCIS cannot approve the I-751 (not even if it was submitted on time, before the deadline). You will have to ask USCIS to convert your I-751 into one with a waiver request. Get in touch with the USCIS's Contact Center for help with this; they might make an appointment for you to visit a local USCIS office.
If your spouse died before the time came to file an I-751, or otherwise never signed an I-751 before death, you can file an I-751 on your own.
Where the form asks for "Basis for Petition," skip the "Joint Filing" boxes and go to the "Waiver or Individual Filing Request" section, then request the waiver by checking the box saying, "My spouse is deceased."
Submit all the evidence that shows that your marriage was bona fide along with your I-751, and a copy of the death certificate.
Typically, an immigrant and U.S. spouse are expected to file an I-751 to remove the conditions on residency within the 90-day period preceding the two-year anniversary of the date the immigrant got a conditional green card.
If, however, your spouse died before you two were able to do that, you can sign and file the I-751 yourself at any time, with a waiver request, based on the death of your spouse. For example, you can file your I-751 long before the usual 90-day period if your spouse died shortly after you became a conditional resident. There's no need to wait until 90 days before the two-year anniversary of your getting conditional residence.
If your spouse died and you've been a conditional resident for less than two years, but are perhaps getting to the end of that time period, it's a good idea to file your I-751 before the two years are up. USCIS keeps track of conditional residents who don't file an I-751 and tries to deport them.
USCIS won't know that your spouse died without you advising it, and might therefore direct Immigration and Customs Enforcement (ICE) to put you into removal (deportation) proceedings before an immigration judge.
You can make those proceedings go away by filing a successful I-751 (since you can file an I-751 with a waiver request at any time), but you obviously want to avoid the cost, inconvenience, and stress of that situation if you can.