Funding
Unlike most other federal agencies, USCIS is funded almost entirely by user fees. Under President George W. Bush's FY2008 budget request, direct congressional appropriations made about 1% of the USCIS budget and about 99% of the budget was funded through fees. The total USCIS FY2008 budget was projected to be $2.6 billion.
Read more about this topic: United States Citizenship And Immigration Services