The IRS will often test your reported income by asking to see your bank statements, etc. to determine how much money is going through those statements and compare it with your reported income. Any difference must be explained. Your lifestyle (home costs, living expenses, etc) must also be supported by your income or you may have to explain and prove where the additional funds to support it come from.
LINK TO AUDIT CRITERIA AND STATISTICS http://www.entrepreneur.com/article/227437.
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