From IRS publication FS-2005-14, “Understanding the Tax Gap.”
Image: Screen_shot_2011-11-04_at_2.58.20_PM.png

Under-reporting noncompliance is the largest component of the tax gap. In other words, non-filing illegals don’t have much to do with the gap caused mainly by taxpayers who are clever enough to cheat on their income, deductions, expenses and credits.