If you are in the United States on a nonimmigrant (temporary) visa, and you need to extend your time in the country or switch to another (also temporary) visa status, the procedure you will likely use is to prepare and submit Form I-539, issued by U.S. Citizenship and Immigration Services (USCIS). (Note that if you're changing to a visa category for work, your employer will likely handle your change of status on its I-129 petition.)
Realize, however, that extensions or changes of status are in no way granted automatically. You'll need to:
We'll cover all of those here.
You must submit your application for an extension or change of status to USCIS before, not after, your old immigration status runs out. This expiration date is most likely shown in the notation the immigration officer made in your passport when you entered the United States. Confirm that date by downloading your I-94 Departure Record and submitting your I-94 with your application.
Do NOT go by the date that your visa (probably stamped into your passport) expires. That is simply the last day you could use that visa for U.S. entry; it's not the date up to which you can stay in the United States.
If you miss the expiration date of your permitted stay and can prove it was not your fault, you can apply late for an extension of status. But you will need to provide documents showing USCIS that you would have met the date but for circumstances beyond your control; that the length of the delay was reasonable; that you haven't violated the terms of your visa status in any other way; and that you aren't just looking for a way to stay in the United States permanently.
Many categories of U.S. visa allow at least one extension, depending on your reasons for needing it, and on your being able to prove your continued "nonimmigrant intent"; that is, that you still plan to leave the U.S. on your designated departure date, not to try to live here permanently. And, provided you have maintained valid visa status (and not violated its rules or terms), chances are good you're allowed to apply for a different status.
But don't assume anything until you've researched the terms of your own visa. Many rules are visa specific—for example, someone on a B-2 tourist visa cannot change to student status unless they got a specific notation on the visa ahead of time. (See, for example, How Long Will Your U.S. Visa Allow You to Stay?.)
Form I-539 is used by a variety of applicants for a variety of requests, so you'll need to read the instructions and questions carefully to narrow in on the requirements that apply to you.
A few questions on the form require extra attention, as follows (referring to the 03/10/21 version of the form):
Part 1, Information About You. If you don't have a USCIS online account number, don't worry about this question; you'd only have such an account if you filed certain types of application and registered for this. For the questions on "Current Nonimmigrant Status" and "Expiration Date," you should be able to find this information on your I-94. For example, if you entered as a vocational student, your "status" would be "M-1." The I-94 will also show a date in most cases; though it might say "D/S" for duration of status if you're a student. That simply means that you can stay until your studies are completed. But if you're no longer studying, then you are out of status and expected to leave the United States.
Part 2, Application Type. This should be self-explanatory, but make sure to mention your family members if they received visas to accompany you to the United States (for example, if you received an F-1 visa and they received F-2s). They too can receive extensions through your filing of this form, but they each need to attach a separate Form I-539A.
Part 3, Processing Information: Do your research ahead of time and make sure you're not asking for more time than will be allowed on your visa extension or new visa. Your request must also be realistic given your needs in the U.S.—and you'll have to back it up with documentation of why you need to stay longer or receive a different visa.
Part 4, Additional Information About the Applicant: If your passport will expire while you are in the U.S. after being granted the extension or change of status, you will need to renew it. The passport must remain valid for at least six months beyond your departure date. And it's important to be able to enter a foreign address here, so that USCIS doesn't think you have pulled up roots and are attempting to live permanently in the United States (a violation of the required "nonimmigrant intent").
In Part 4 Questions 3-15, you should be able to answer "No" to all the questions. If you answer "Yes" to any, you are most likely inadmissible, and will not receive a visa. The exception is that certain visa categories allow dual intent for people seeking labor-based visas, including the H-1B, L, and O-1 visas. Consult a lawyer for any other situation where your answer is yes, particularly for the criminal background questions and question about having worked in the United States.
If you are in the U.S. on a J-1 visa, you should also consult a lawyer, as your rights to change your status are complex and limited.
If including family members in your application, be sure to submit a separate I-539A form for each.
Again, you'll need to pay careful attention to the instructions. In most cases, you'll need to supply:
Mail your application to the address shown in the USCIS instructions. If you have any questions about your eligibility, or how to fill out the form and prepare the application, consult an immigration attorney.