Colorado’s largest teachers union is calling for corporations to pay more to fund education, but left the details largely undefined in a new report released Thursday.

The “Final Countdown” report is light on details about what “tax breaks and incentives” the Colorado Education Association wants to see eliminated, or whether it thinks such changes could come close to raising the $8.1 billion needed to pay off the “negative factor” that’s built up in the state budget since 2009.

The negative factor is essentially an IOU — an acknowledgment that a court ordered the state to increase school funding, but lawmakers haven’t found the money to do so.

The 12-page report said Colorado’s teacher pay and per-pupil funding both ranked in the bottom 10 in the country. While Colorado spends more on schools than it did 30 years ago, it hasn’t kept up with other states that further raised their per-pupil funding.

CEA President Amie Baca-Oehlert said the union isn’t proposing a specific bill at this point, but will work with lawmakers when they return in January to find more revenue for education. In a survey, members said their top priority is raising pay, though they also want to reduce class sizes and bring in more mental health supports for students, she said.

“Corporations are receiving tax breaks while we’re underfunding our schools,” she said.

Getting rid of deductions or exemptions to fund education may not be easy, even if lawmakers were to like the idea.

The Taxpayer Bill of Rights limits the state’s ability to raise taxes, though court cases suggest the legislature could eliminate exemptions so long as they didn’t generate enough new revenue to force tax refunds, said Carol Hedges, executive director of the Colorado Fiscal Institute. In practice, that means closing exemptions likely wouldn’t produce new revenue under the current framework — it would just replace money the state isn’t taking in if the economy slows down, perhaps preventing further cuts to education, she said.

“It’s a little murky,” Hedges said.

The report also called for a minimum salary for teachers and support staff, based on cost-of-living in each district. Baca-Oehlert said the union wasn’t taking a position on how exactly to do that, but would have conversations with lawmakers.

The state already gives more funding to districts with a higher cost of living, but districts aren’t required to spend that money on salaries. Basing school funding on cost-of-living also has its critics, who argue it gives more advantages to wealthy resort towns.

School funding disputes have led to three teacher strikes in the past two years, in Pueblo, Denver and Fairplay. About half of union members who took part in a poll said they’d be willing to participate in a strike to raise education funding statewide, Baca-Oehlert said. About one-third weren’t interested in a strike, but said they would be willing to participate in a shorter-term walkout, she said.

“Our hope is that we don’t have to get to that,” she said.