The tax system collects its due, even from a class of workers with little likelihood of claiming a refund and no hope of drawing a Social Security check.

Illegal 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.