It's a myth that illegal immigrants don't pay taxes; while the IRS does not have an estimate of how many illegal immigrants pay income tax, it has been issuing ITINs to foreigners without a SSN# since 1996 so by using her itin, she/ other undocumented illegal residents can pay tax to the irs/state; however, in this particular case, she is a us resident, not an illegal alien, as she married a us citizen, your friend, and can file return as us resident.aslongasd she is still married on the last day of the year, then she can file MFJ and take advantage of the small but helpful tax breaks given to married couples |