Do I Need to File My Marriage-based AOS before My Non-immigrant Visa Expires
Remaining in the US after your nonimmigrant visa expires can carry some lofty consequences. Generally you cannot apply to adjust status without a valid visa. However, if you are married to a US citizen, in most circumstances you are still eligible to adjust status after your visa expires. US Immigration law has carved out an exception for immediate relatives (spouse, parent or child under 21) of US citizens.
Example: You are visiting from the U.K. on a B-2 visitor visa. Your B-2 visa expires but you are married to a US citizen. You are able to adjust status even after your visitor visa expires.
However, it is important to keep in mind that, if your marriage to the US citizen ends before you adjust status, you will no longer be eligible to adjust through them and you will have accrued unlawful status. Therefore, it is important to consult an attorney before your status expires to advise you on the consequences of an overstay in your particular situation.
Note: If you entered on a K-1 (fiance) visa and did not get married within 90 days, you will be ineligible to adjust even if you marry a US citizen.