"Tax Evasion" literally means evading the burden of taxes, i.e. not paying the tax u r liable to pay to the Government on ur total income BY hiding ur income or not disclosing true and relevant facts regarding sources of ur income. If u have heard of "black money", it is infact a form of tax evasion. Incomes on which have not been disclosed and on which taxes have not been paid is termed as black money.