Tax evasion is the general term for efforts to not pay taxes by illegal means.  Tax evasion usually entails taxpayer deliberately misrepresenting or concealing the true state of their affairs to reduce their tax liability.  Tax evasion requires a willful intent on the part of the taxpayer. 

Tax evasion does NOT include a taxpayers attempt to avoid or minimize their tax liability by utilizing exemptions, deductions and exclusions granted by law.  The distinction between tax avoidance and tax evasion is the reason taxes are extremely complex and often require forensic accountants to reconstruct financial transactions to determine the difference between tax evasion and tax avoidance.