13 Constitutional Limitations on Taxation

[A] Those directly affecting taxation
[1] Prohibition against imprisonment for nonpayment of poll tax
[2] Uniformity, equability and progressivity of taxation
[3] President's authority to impose tariff rates, wharfage dues, tonnage dues and import and export quotas (flexible tariff clause)
[4] Exemption to religious, charitable and educational institutions regarding property used actually, directly and exclusively for such purpose, regardless of who the owner is
[5] Item veto of the President
[6] Non-impairment (increase or decrease) of the jurisdiction of the Supreme Court
[7] Power of local governments to create own sources of revenue
[8] Ban on appropriation for use of public money for religious purposes
[B] Those indirectly affecting taxation
[9] Due process of law
[10] Equal protection of law
[11] Religious freedom clause
[12] Non-impairment of obligations and contracts (inviolability of contractual tax exemptions)