When something goes wrong
How long can I stay, and what if I file late?
Your legal stay ends on the Admit Until date on your I-94. To extend, USCIS must receive your I-539 before that date — file early (they suggest up to 45 days ahead). Staying past your authorized date without a timely, pending application can lead to "unlawful presence", which carries serious consequences. The assistant shows your days remaining and recommended file-by date, but how a late or already-expired situation is handled is a legal-judgment question — talk to a licensed immigration attorney.
What if…
My status already expired — what now?
This is exactly the kind of situation that needs a licensed immigration attorney. There may still be options in limited circumstances, but they depend on facts only an attorney should weigh. Do not file on a generic assumption — get advice first.
Official sources
This is general information, not legal advice.