Under Philippine taxation law, a tax is considered valid if it meets certain essential requisites grounded in constitutional and statutory mandates. These requisites ensure that taxation remains fair, just, and equitable while supporting the government’s financial needs. The requisites of a valid tax can be classified under four primary categories: (1) Public Purpose, (2) Uniformity and Equality, (3) Legislative Imposition, and (4) Compliance with Due Process and Equal Protection Clauses. Here is a meticulous examination of each of these elements in the context of Philippine taxation law:

1. Public Purpose

A valid tax must serve a public purpose. This principle is derived from the fundamental doctrine that taxes are primarily imposed for the benefit of the public at large rather than for the advantage of private individuals. The public purpose requirement mandates that taxes collected by the government be used for activities that support the welfare of the state and the general population, such as infrastructure, education, health, defense, and social services. In the landmark case Pascual v. Secretary of Public Works (1960), the Supreme Court ruled that funds raised from taxation must not be used for private purposes; rather, they must directly or indirectly benefit the public.

The broad interpretation of "public purpose" has evolved over time, encompassing even projects and activities that may not appear directly beneficial to every taxpayer but contribute to overall societal progress. Philippine courts generally defer to the discretion of Congress on matters of public purpose, as it is primarily a question of policy, but the judiciary may intervene when a clear abuse of this principle is evident.

2. Uniformity and Equality

Tax laws must be uniform and equitable. This means they must apply equally to all persons or entities within the same class. Uniformity requires that persons or entities belonging to the same category or class be treated equally in terms of the tax rate and assessment. Equality, on the other hand, implies that tax burdens should be imposed fairly, recognizing distinctions where appropriate, to prevent unfair taxation.

The Uniformity Clause in the Philippine Constitution (Article VI, Section 28) mandates that taxes must be "uniform and equitable." In Philippine Trust Company v. Yatco (1945), the Supreme Court explained that uniformity in taxation does not mean that everyone must pay the same amount; rather, individuals in similar situations should be taxed similarly, thus ensuring fairness in the tax system.

However, classifications in tax law are permitted as long as they are reasonable and based on substantial distinctions. For instance, corporate taxes differ from personal income taxes due to the inherent differences in income generation. In Commissioner of Internal Revenue v. Fireman’s Fund Insurance Co. (1991), the Court upheld the validity of a tax that classified taxpayers differently based on their income sources, emphasizing that reasonable classifications do not violate the uniformity rule.

3. Legislative Imposition

A tax must be legislatively imposed. The power to tax is inherent in the sovereignty of the State, but in the Philippines, it is vested in Congress. Article VI, Section 28(1) of the 1987 Philippine Constitution provides that “The rule of taxation shall be uniform and equitable. The Congress shall evolve a progressive system of taxation.” This grants Congress the exclusive authority to enact tax laws.

Legislative imposition is a safeguard against arbitrary and unauthorized taxation by non-legislative entities. Under Local Government Code of 1991 (Republic Act No. 7160), local governments are empowered to impose local taxes, fees, and charges within their respective jurisdictions, although their power is subject to limitations imposed by the national government.

Congress has the power to delegate taxing authority to administrative bodies, such as the Bureau of Internal Revenue (BIR), to prescribe details for implementing tax laws, provided the delegation is clear and complete and contains sufficient standards. The Court held in Maceda v. Macaraig, Jr. (1991) that such delegations are constitutionally permissible when clear guidelines are present, as they aid the BIR in effectively implementing tax statutes.

4. Due Process and Equal Protection Clauses

Tax laws must respect due process and equal protection. The Due Process Clause requires that tax laws must not be arbitrary or oppressive; they should be reasonable and fair. Taxes should not amount to confiscation of property and should not be unduly harsh. In Ormoc Sugar Company, Inc. v. Treasurer of Ormoc City (1968), the Supreme Court ruled that tax laws must provide taxpayers an opportunity to be heard and that they cannot be retroactively applied in a way that would unfairly deprive taxpayers of their property without due notice.

The Equal Protection Clause mandates that tax laws must not discriminate unfairly between similarly situated taxpayers. While taxation often involves classifications, these classifications must be reasonable, not arbitrary, and must serve a legitimate governmental purpose. In Pepsi-Cola Bottling Co. of the Philippines, Inc. v. City of Butuan (1967), the Court struck down a tax ordinance for imposing a higher tax rate on a specific industry without a reasonable basis, as it violated the equal protection guarantee.

Courts use the rational basis test to assess whether classifications within tax laws are constitutionally valid, requiring that distinctions in tax treatment must have a logical foundation in serving legitimate government objectives.

Additional Requisites and Jurisprudential Considerations

Non-Delegability of the Power to Tax: The power to tax is primarily a legislative function and, as a general rule, cannot be delegated. However, as discussed, Congress may delegate the power to ascertain and prescribe details for tax implementation to administrative agencies, provided it remains within well-defined limits and standards.
Prohibition against Double Taxation: While not explicitly prohibited by the Constitution, double taxation is generally disfavored unless there is a clear legislative intent. Courts in the Philippines have viewed double taxation as imposing two taxes on the same property, in the same amount, for the same purpose, by the same authority, within the same period. This was addressed in City of Manila v. Coca-Cola Bottlers (1999), where the Supreme Court noted that double taxation does not necessarily invalidate a tax law unless it results in oppression or violates constitutional protections.
Non-Impairment of Contracts: Under Article III, Section 10 of the Philippine Constitution, the power to tax cannot impair obligations under valid contracts. In Shell Philippines, Inc. v. Commissioner of Internal Revenue (1996), the Court reiterated that the government cannot impose a new tax or increase an existing one in a way that would substantially impair contractual obligations unless it serves a legitimate public purpose.
Progressive Taxation Principle: The Constitution mandates that the tax system be progressive, meaning tax rates should increase as the tax base (income or wealth) increases. Progressive taxation aims to distribute the tax burden more equitably across socio-economic classes, ensuring that those with higher incomes contribute a larger proportion of their resources to government revenues.
Revenue vs. Regulatory Taxation: Taxes are generally classified as either for revenue generation or for regulation. A revenue tax primarily aims to raise funds, while a regulatory tax seeks to achieve social or economic policy objectives, such as discouraging harmful activities (e.g., "sin taxes" on alcohol and tobacco). Both types are valid as long as they satisfy the requisites of public purpose, uniformity, and due process.
Fiscal Adequacy: The government’s tax collection must meet the demands of government expenditures, a concept known as fiscal adequacy. This requisite, though not explicitly listed among constitutional requirements, is crucial in determining the effectiveness and sustainability of tax policies.

Conclusion

The requisites of a valid tax in Philippine law are meticulously grounded in constitutional and jurisprudential doctrines. Public purpose, uniformity and equality, legislative imposition, and adherence to due process and equal protection are foundational principles that ensure the government’s power to tax is exercised fairly, equitably, and responsibly. These requirements collectively safeguard taxpayers’ rights while supporting the government’s capacity to fund programs essential for public welfare and development.