As per law, three months imprisonment is the minimum sentence for tax evasion, and 7 years imprisonment is the maximum sentence for tax evasion . You can read about the Black Money, Tax-Evasion & Tax-Avoidance in the given link.
The punishment depends on the amount of tax under reported or evaded.
- Double Taxation Avoidance Agreements (DTAA) – Countries Involved, Income Tax Provisions
- UPSC Mains General Studies Paper-III Strategy, Syllabus & Structure