You pretty much answered it yourself.u00a0 Yes, the 30% withholding is just that, withholding.u00a0 Until you file the tax return, the Feds have it, and are under no obligation to return it to you if you don't file a return.u00a0 So, yes a 30% tax on those that don't file their return.u00a0 It likely is to cover the fact that many NRA's likely don't file returns.