A 3% tax on individual income over $1 million would flood Illinois’ coffers with at least $4.5 billion in new revenues annually, a new state estimate shows weeks ahead of an advisory referendum on earmarking that money for property tax relief.The estimate, obtained by WBEZ through a state open-records request, marks the first time Gov. JB Pritzker’s Revenue Department has weighed in on the effects of imposing that new proposed tax on the state’s wealthiest citizens to ease what is a leading financial issue daunting the middle class.Voters are being asked this question now because lawmakers in May voted to bring it forward as part of a broader election package that Pritzker signed.The exact wording of the ballot question reads: “Should the Illinois Constitution be amended to create an additional 3% tax on income greater than $1,000,000 for the purpose of dedicating funds raised to property tax relief?”And while the results on the referendum won’t be binding, the outcome could arm policymakers in the General Assembly with new ammunition to seek a constitutional amendment in 2026 — the year Pritzker himself may be on the ballot — to impose the millionaires tax for property tax relief.“There’s a huge hue and cry for the reduction of property taxes in Illinois. It’s the most regressive type of tax. And I think what we want to make sure of is that if we’re going to do something regarding property tax relief and utilizing the surcharge for individuals who make more than $1 million, the general public supports it,” said state Rep. Jay Hoffman, D-Collinsville, chief House sponsor of the May legislation that put this question to voters.“I’m hopeful that they will,” he said.South suburbs hard-hit by property tax increasesProperty taxes in Cook County have skyrocketed this year. An analysis by Cook County Treasurer Maria Pappas’ office found homeowners in the south and southwest suburbs of Chicago being hit with a record 19.9% median increase in property tax bills.She cited some examples in 15 south suburbs where property tax increases for homeowners exceeded 30% this year.State Revenue Department estimates show that for the 2021 tax year, the most recent year available, there were 77,323 Illinoisans who reported having adjusted gross income greater than $1 million annually.The November ballot question seeking input on whether to make that group pay more is not the first time Illinois voters have been surveyed on the issue, and the votes have yielded seemingly contradictory outcomes.Pritzker’s plan to change the state Constitution so wealthy Illinoisans would pay higher income tax rates than those making less failed in 2020, drawing less than 47% support. It marked a rare but significant defeat for Pritzker, who went toe-to-toe with another state billionaire, Kenneth Griffin, who poured $54 million of his own money into defeating the ballot initiative.Six years earlier, though, voters were in a different mood. In 2014, another advisory referendum taking aim at state millionaires was on the ballot. It sought input on whether revenues derived from a new 3% tax on income in excess of $1 million should go toward schools — and 64% of voters favored doing so.Hoffman said if the 2024 question passes and encourages making millionaires shoulder a heavier burden in supporting government services, there will be inevitable constitutional questions. The state constitution calls for a flat income tax, and that likely would have to be changed.“If it were to pass overwhelmingly, then we need to sit down with Illinois constitutional experts to figure out what the next step would be,” Hoffman said. “If it would require a constitutional amendment to be on the ballot in a couple of years, I certainly would be in favor of putting that on the ballot.”Republicans oppose the non-binding referendumThis fall’s advisory question is not drawing GOP support. House Minority Leader Tony McCombie, R-Savanna, for example, said she intends to vote against the advisory referendum.“Illinois already had a referendum on raising taxes (aka graduated income tax), which voters overwhelmingly rejected,” said Colleen King, a spokeswoman for the Republican legislative leader, in an email to WBEZ. “Collectively, Illinoisans are one of the highest taxed in the nation. Increasing taxes will not lead the state to more economic opportunity.”While Pritzker signed the legislation authorizing next month’s referendum, whether the governor himself intends to vote for it is unclear. A campaign aide avoided a direct answer to that question when asked by WBEZ.“Gov. Pritzker has always stood firm in his belief that Illinois needs a tax code that treats our middle class families more fairly — a nurse shouldn’t be paying the same tax rate as someone making millions of dollars a year,” Pritzker campaign spokeswoman Christina Amestoy said in a statement.“It’s why he’s delivered tax relief for Illinois families, from eliminating the grocery tax to increasing education funding so local municipalities can lower property taxes,” she said.If a 3% tax on earnings beyond $1 million had been in effect for the 2022 tax year — the most recent year for which Illinois’ billionaire governor and his wife have made their taxes public — he and MK Pritzker would have paid an additional $37,535, a WBEZ analysis shows.Pritzker’s Democratic predecessor, former Gov. Pat Quinn, has not been shy about advocating for the ballot question.“This is the first time Illinois voters have a chance to vote on a specific measure to fund property tax relief for over 3 million households in our state,” Quinn said.“Illinois has the second highest property taxes in the country. It’s hammering a lot of folks who live from paycheck to paycheck, and getting a property tax relief referendum on the ballot is the voice of the people and the voice of the taxpayers,” he said. “That’s the way you win reforms and relief that are long overdue.”Dave McKinney covers Illinois government and politics for WBEZ and is the former longtime Springfield bureau chief for the Chicago Sun-Times.