Generally if a nonimmigrant overstays the period authorized by his/her visa, the visa is void under INA § 222(g). Persons subjected to § 222(g) cannot be readmitted to the U.S. except by returning to the consular office in the country of their nationality to obtain another visa. There are exceptions.
Change of Status or Extensions of Stay
By timely filing a Change of Status or Extension of Stay a nonimmigrant (who has not worked without authorization) will be considered to be in lawful status while the application is pending. The application must not be frivolous (lacking an arguable basis in law/fact).
Process for Requesting Extension of Stay:
The procedure is governed by 8 CFR §214.1(c)(2):
1. Using Form I-539 apply at USCIS service center. However, temporary workers (E, H, L, O, P, Q, R, TN) use Form I-129.
2. The application is timely if filed before the expiration of current status.
3. Provide reasons requesting stay and attach I-94 with documentation. You must keep your passport current during extension period.
4. Bridge filing are not permitted.
5. Out-of-Time requests may be granted by USCIS nunc pro tunc where the failure to timely file was due to extraordinary circumstances outside the applicants control, the delay was commensurate with the circumstances, the applicant is a bonafide nonimmigrant visa holder not in removal proceedings, and has not otherwise violated visa status. 8 CFR §214.1(c)(4).