The spouse or a dependent of the principal alien must serve as the applicant. If the dependent is under-age, the principal alien can sign on his/her behalf.

Part 2, Q.2b: If more than one applicant, use Supplement-1 for the additional applicants.

Part 3, Q.1: Request the same expiration date as the principal alien under most circumstances.

Part 3, Q.2: If the principal alien already has received an extension or change of status, be sure to insert the VSC, LIN, SRC, or WAC number of that filing. These initials relate back to the old names of the U.S. Citizenship and Immigration Services (USCIS) Service Centers, with EAC being Vermont Service Center, LIN being Nebraska Service Center, SRC being Texas Service Center, and WAC being California Service Center.

Part 3, Q.3: Do your best to submit the I-539 with the principal's I-129. However, do not await the results of the I-129 filing if doing so will mean that the spouse or dependents will overstay or lose their status.

Part 4, Q.3: If the principal has O-1B status, it does not matter what the answer is to subparts a or b. Otherwise, though, a "yes" answer to any of these questions should prompt a call to an immigration attorney. On the support question under subpart 3f, insert "Spouse [or parent] in O-1B [or O-2, etc.] status is sole source of support."