Quoting beatthegame Okay, either way I need to provide my employer SSN, but could the employer withhold my last paycheck for tax purpose? I am on my OPT Ah, now the salient details. You are on an F-1 visa with OPT. Give them your SSN. There's no reason not too. Anyhow, the next question that now needs to be asked. Are you working for an outside company or some part of your school?