It is relatively easy for the IRS to verify the returns and reported income of taxpayers whose income results from wages, interest and dividends, and who take the standard deduction, who comprise the majority of taxpayers, ... It is harder, and often requires audits, to verify the income of taxpayers with other forms of income and deductions.  -   Charles Rossotti     Quotes
It is relatively easy for the IRS to verify the returns and reported income of taxpayers whose income results from wages, interest and dividends, and who take the standard deduction, who comprise the majority of taxpayers, ... It is harder, and often requires audits, to verify the income of taxpayers with other forms of income and deductions. Charles Rossotti