In 1985, Oklahoma voters approved State Question 588 by a 69.7 percent majority. This created the ad valorem manufacturing exemption. Under Article X, Section 6B of the Oklahoma Constitution, all real and personal property that is necessary for the manufacturing of a product and facilities engaged in research and development, which meet certain requirements, receive a five-year exemption from ad valorem (property) taxes. Since 1985, the range of entities eligible for the exemption has been expanded.
The law says that the state will reimburse local recipients of ad valorem taxes, such as counties and school districts, for the full amount of lost revenue under the exemption. The cost of the exemption has grown to $134.4 million in Tax Year 2017, up from $37.8 million in 2011, and the cost has increased seven-fold since 2000. In 2018, 45 percent of the total exemption was claimed by electric wind generation, with traditional manufacturing (25 percent) and computers (21 percent – all attributable to the Google plant in Mayes County) being the next largest categories. As a result of legislation passed in 2015, wind producers are no longer able to claim the ad valorem exemption for facilities developed after 2016
One percent of state personal income tax revenue goes to the Ad Valorem Reimbursement Fund to cover the cost of the exemption. This fund typically falls far short of what is needed. In most years, this leads to a supplemental appropriation to schools for lost property tax revenue; for FY 2019, the supplemental hit $99.6 million.