Ultra-wealthy Illinois residents would see their tax bills jump three percentage points under a progressive income tax framework released by Gov. J.B. Pritzker (D) March 7.

And corporations would pay nearly a percentage point more in income taxes under Pritzker’s proposed “fair tax plan.”

For the first time since taking office in January, Pritzker laid out his plan for solving the state’s fiscal crisis through a strategy junking its constitutionally protected flat income tax and replacing it with a graduated system. The resulting fair tax structure would generate $3.4 billion annually, permitting the state to fill a $3.2...