Illegal immigrant do pay taxes.
Many pay income taxes. Some do so using a fake Social Security number. Other do so with a Taxpayer Identification Number.
Illegal immigrant also pay Social Security taxes. Stephen C. Goss, the chief actuary of the Social Security Administration, states that in 2007 alone, illegal immigrant payed some $12 million dollars into the Social Security trust fund. Most will not see a penny of these contributions, yet their contributions are paying for the retirement of precisely the people who are most anti-immigrant.
Illegal immigrants also pay sales taxes and other taxes.