The doctrine of legitimate expectations in tax law is examined as an institution of public-law nature. Drawing on judicial practice and recent legislative amendments, the study identifies systemic implementation defects: the absence of unified criteria, the insufficiency of compensatory mechanisms, and the inconsistency of judicial interpretations. It proposes statutory enshrinement of the doctrine, unification of law enforcement through a plenary ruling of the Supreme Court of the Russian Federation, and the introduction of preventive procedures. The article substantiates that safeguarding legitimate expectations constitutes a fundamental precondition for the stability of the tax legal order and the trust-based character of tax legal relations.