According to the Internal Revenue Service, almost one-fifth of taxpayers violate the tax code in some way each year.  Individual taxpayers rather than corporations commit the majority of these violations.  However, unless there are signs of fraud, the IRS will usually assume that a mistake has been made through either negligence or careless error.  When tax auditors find suspicious activity, the IRS Criminal Investigation section will launch an investigation to determine if the acts were tax fraud or simply negligence.  Penalties for tax fraud may include fines and/or imprisonment.

For more read, “Income Tax: Fraud vs. Negligence.”