A creature of statute: no tax without a law identifying its subject, rate, payer and time — the legality principle (Article 115's principle in Nepal's Constitution: no tax except by law). The Supreme Court has struck levies imposed by executive order or by delegated legislation beyond the statute's letter. An inherent sovereign power: every sovereign state's taxation power is inherent — but in a constitutional state it is held by the REPRESENTATIVE legislature (the people's house), and the executive has no free discretion over it: where the law is silent or ambiguous, the benefit goes to the taxpayer (the Court's settled approach — Mahendra Raj Pandey v. Nepal Rastra Bank, writ 2677 of 2062). Public law, administrative operation: taxation is public law — the taxpayer is not a party to a bargain but a subject of a statute; yet a statute that itself grants rights (appeal, refund, hearing). Non-punitive and proportionate: a tax law must not be confiscatory — the Court has held that a levy unreasonable in principle (a cinema tax on seats rather than ticket sales) fails constitutional discipline; the rate and base must be justifiable.
Prospective: tax laws speak from their commencement; retrospective taxation is exceptional and must be express — the Court's consistent line.