When many people come to the same "assumption" there may be some data that suggests that assumption is correct. On the other hand, you're simply denying what appears to be the truth without giving any reason why you think the experts' numbers are wrong.
Last time I looked at my pay stub, the state withheld money for taxes they expect me to owe, as well as the feds.
http://californiawatch.org/watchblog/illegal-immigrants-pay-their-taxes-study-finds
Illegal immigrants pay their taxes, study finds
In the continued debate over immigration, some proponents of a new amnesty program make an economic argument: By legalizing illegal immigrants who have come to the U.S. to work, a torrent of new tax revenue will flow into government coffers, they say.
But a study by the Public Policy Institute of California released Tuesday night says that when it comes to paying taxes, illegal immigrants are already doing their share.
“Illegal immigrants already pay sales taxes and many contribute to Social Security,” according to a PPIC study based on data from the PPIC’s New Immigrant Survey. It draws on information from a sample of former illegal immigrants who became legal permanent residents in 2003.
“The vast majority of illegal immigrants already file federal tax returns,” a report summary says.
“In the year before acquiring legal status, 87 percent of those who had crossed the border illegally and 91 percent of those who had overstayed their visas filed federal returns.”
http://www.usatoday.com/money/perfi/taxes/2008-04-10-immigrantstaxes_N.htm
llegal immigrants are paying taxes to Uncle Sam, experts agree. Just how much they pay is hard to determine because the federal government doesn't fully tally it. But the latest figures available indicate it will amount to billions of dollars in federal income, Social Security and Medicare taxes this year. One rough estimate puts the amount of Social Security taxes alone at around $9 billion per year.
Paycheck withholding collects much of the federal tax from illegal workers, just as it does for legal workers.
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The Social Security Administration estimates that about three-quarters of illegal workers pay taxes that contribute to the overall solvency of Social Security and Medicare.
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In 2006, then IRS Commission Mark Everson told Congress that "many illegal aliens, utilizing ITINs, have been reporting tax liability to the tune of almost $50 billion from 1996 to 2003."
http://reason.org/news/show/122411.html
Illegal Immigrants are Paying a Lot More Taxes Than You Think
Denying public services to people who pay their taxes is an affront to America's bedrock belief in fairness. But many "pull-up-the-drawbridge" politicians want to do just that when it comes to illegal immigrants.
The fact that illegal immigrants pay taxes at all will come as news to many Americans.
A stunning two-thirds of illegal immigrants pay Medicare, Social Security and personal income taxes. Yet, nativists like Congressman Tom Tancredo, R-Colo., have popularized the notion that illegal aliens are a colossal drain on the nation's hospitals, schools and welfare programs — consuming services that they don't pay for.
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One might have imagined that those fearing deportation or confronting the prospect of paying for their safety net through their own meager wages would take a pass on the IRS' scheme. Not so.
Close to 8 million of the 12 million or so illegal aliens in the country today file personal income taxes using these numbers, contributing billions to federal coffers. No doubt they hope that this will one day help them acquire legal status — a plaintive expression of their desire to play by the rules and come out of the shadows.
What's more, aliens who are not self-employed have Social Security and Medicare taxes automatically withheld from their paychecks. Since undocumented workers have only fake numbers, they'll never be able to collect the benefits these taxes are meant to pay for. Last year, the revenues from these fake numbers — that the Social Security administration stashes in the "earnings suspense file" — added up to 10 percent of the Social Security surplus. The file is growing, on average, by more than $50 billion a year.
(a point in all three of these articles is that these people are paying into the system and getting back far less than the rest of us do)