Article XIII, § 26

(a) Taxes on or measured by income may be imposed on persons, corporations, or other entities as prescribed by law. (b) Interest on bonds issued by the State or a local government in the State is exempt from taxes on income. (c) Income of a nonprofit educational institution of collegiate grade within the State of California is exempt from taxes on or measured by income if both of the following conditions are met: (1) The income is not unrelated business income as defined by the Legislature. (2) The income is used exclusively for educational purposes. (d) A nonprofit organization that is exempted from taxation by Chapter 4 (commencing with Section 23701) of Part 11 of Division 2 of the Revenue and Taxation Code or Subchapter F (commencing with Section 501) of Chapter 1 of Subtitle A of the Internal Revenue Code of 1986, or the successor of either, is exempt from any business license tax or fee measured by income or gross receipts that is levied by a county or city, whether charter or general law, a city and county, a school district, a special district, or any other local agency.