According to a Treasury report (https://home.treasury.gov/system/files/136/The-American-Families-Plan-Tax-Compliance-Agenda.pdf), the tax gap, which is the spread between what the federal government collects in taxes and what it thinks it should be collecting, continues to grow. The tax gap is now estimated to be $584 billion, which is about 3% of GDP each year in owed but uncollected taxes. The tax gap could rise to $7 trillion over the next decade if it isn’t addressed.
The tax gap results from:
The Treasury suggested several ways to increase tax compliance:
Tax paid by self-employed persons to finance Social Security coverage. In 2007, there are two rates. A 12.4% rate applies to a taxable earnings base of $95,700 or less and a 2.9% rate applies to all net earnings.