Canons of Taxation are principles for good tax design (Adam Smith). Principle of Equality: Subjects should contribute in proportion to abilities; proportional and fair burden distribution. Principle of Certainty: Timing, amount, manner of payment clear to taxpayer; reduces uncertainty and compliance costs. Principle of Convenience: Taxes collected when taxpayer has means to pay; collection methods convenient; reduces hardship. Principle of Economy: Low administrative costs; revenue should far exceed collection costs; minimizes deadweight loss. Modern additions: Simplicity (easy to understand), Efficiency (minimal economic distortion), Sustainability (revenue stable over time), Transparency (open about tax usage). Application in practice: Progressive rates address equity; regular collection schedules address convenience; standardized forms address certainty; efficient administration addresses economy. Indian context: GST aimed at certainty and economy; income tax progression addresses equality; withholding at source ensures convenience. Violations: Arbitrary taxes violate certainty; corrupt administration violates economy; regressive systems violate equality. ICAI focus: Understanding each canon, identifying violations in tax systems. Exam tip: These five canons are classic; modern questions may add sustainability and environmental taxes.