I meant to say that she will be out of status after the OPT expires. You did not mention about her H-1B before so I didn't know the facts very well. I didn't know that she was employed too. Yes, I-539 changes her status to H-4. You guys are lucky that her OPT expires in October, that's when the H-1B visa starts. So you could wait until the end of September to see if the H-1B visa from HER employer gets approved or not. If it does not get approved, then you can file I-539 to change her status to H-4. But for right now, she is already in good shape. If she is employed tell her that she does not need to pay Social and Medicaid tax under OPT. You just have to pay federal and/or state tax.