This book explains the extent, limit and content of the power of an executive authority which has to be exercised judicially, fairly, justly, and according to the rule of laws, i.e. rule of reason, rule against arbitrariness and discrimination, rules of fair play and natural justice. it explains such concepts are judicial reviews, jurisdiction, discretionary powers, and doctrines such as natural justice, legitimate expectation, promissory estoppels and burden of proof with the help of the decisions of the Indian and foreign courts. This is done by taking income-tax statute as the base.