The protest comes less than a week after the City Council approved Mayor Rahm Emanuel's budget, which includes a $588 million property tax increase.
"You and I will soon pay 10.25 percent sales tax at the store," said Toby Chow of Fair Economy Illinois. "Right now, big banks and corporations buying stocks and futures in Chicago don't pay a cent. A tiny sales tax amounting to less than .002 percent of the average contract value would scarcely be noticed by the big corporations, but it would generate billions of dollars for vital resources that we need in our communities."
Activists are blocking the entrances to the building on West Jackson.
Hundreds of protesters gathered for the demonstration Monday morning, with some estimates on Twitter putting the crowd at 1,000 people or more. Police began arresting activists shortly before noon.
Moral Mondays Illinois, which is organized by Fair Economy Illinois, said in a press release they are demanding the tax "in order to raise billions of dollars to fund schools, streets and public transit, pensions for public workers, health care, child care and other social safety net programs."
Moral Mondays protesters have previously protested on LaSalle Street and Michigan Avenue, and taken over the lobbies of Citadel, Morningstar and real estate mogul Sam Zell. Opponents of the trading tax say it will drive the exchanges out of Illinois, but Fair Economy Illinois says the tax will not be on the exchanges themselves but instead the trading activity of big banks and corporations.