From the summary:
This report provides state-by-state estimates on the state and local tax contributions of the 11.2 million undocumented immigrants living in the United States.
The key findings are:
• Undocumented immigrants currently contribute significantly to state and local taxes, collectively paying an estimated $10.6 billion in 2010 with contributions ranging from less than $2 million in Montana to more than $2.2 billion in California. This means these families are likely paying about 6.4 percent on average of their income in state and local taxes.
• Allowing undocumented immigrants to work in the United States legally would increase their state and local tax contributions by an estimated $2 billion a year. Their effective state and local tax rate would also increase to 7 percent on average, which would put their tax contributions more in line with documented taxpayers with similar incomes.