Lisa Christensen Gee, JD, Senior Policy Analyst, Matthew Gardner, Executive Director, and Meg Wiehe, MPA, State Tax Policy Director for the Institute on Taxation and Economic Policy (ITEP) in a Feb. 2016 report, “Undocumented Immigrants’ State and Local Tax Contributions,” available at itep.org, stated:
"Undocumented immigrants contribute significantly to state and local taxes, collectively paying an estimated $11.64 billion a year. Contributions range from almost $2.2 million in Montana with an estimated undocumented population of 4,000 to more than $3.1 billion in California, home to more than 3 million undocumented immigrants.
Undocumented immigrants nationwide pay on average an estimated 8 percent of their incomes in state and local taxes (this is their effective state and local tax rate). To put this in perspective, the top 1 percent of taxpayers pay an average nationwide effective tax rate of just 5.4 percent.