Illegal immigration costs U.S. taxpayers about $113 billion a year at the federal, state and local level.  The annual outlay that illegal aliens cost U.S. taxpayers is an average amount per native-headed household of $1,117.

  Education for the children of illegal aliens constitutes the single largest cost to taxpayers, at an annual price tag of nearly $52 billion.

  At the federal level, about one-third of outlays are matched by tax collections from illegal aliens. At the state and local level, an average of less than 5 percent of the public costs associated with illegal immigration is recouped through taxes collected from illegal aliens.

Most illegal aliens do not pay income taxes. Among those who do, much of the revenues collected are refunded to the illegal aliens when they file tax returns. Many are also claiming tax credits resulting in payments from the U.S. Treasury.

http://www.fairus.org/publications/the-fiscal-burden-of-illegal-immigration-on-united-states-taxpayers