The notice allows the strike to happen at any time after 10 days.
A strike date will likely be discussed at the union's House of Delegates meeting which is set to take place Thursday. That means Chicago Public School teachers could strike as early as the second week of school.
"CPS seems determined to have a toxic relationship with its employees. We have been belittled, bullied, and betrayed by this administration," said Karen Lewis, president, Chicago Teachers Union.
The move to file a 10-day strike notice comes after nine months of negotiations.
Despite nearly 50 bargaining sessions, the head of the union said Wednesday the two sides hadn't even gotten to some major issues, including wages.
"This is a difficult decision for all of us to make. But this is the only way to get the board's attention," said Lewis.
Key sticking points include how to staff the longer school day as well as the issue of merit pay, essentially tying teachers' raises to student performance.
Before the strike notice had been filed, Lewis said merit pay has never been on the table.
"We have never discussed merit pay with teachers, let me be clear about that. We've talked about different ways of looking at compensation, but never discussed merit pay with teachers," said Jean-Claude Brizard, Chicago Public Schools CEO.
The union literally scoffed at that claim.
"How would he know? He's never been there," said Lewis.
"This 10-day notice will put pressure on our kids and our families, which we don't need, but we have been very serious about coming to a resolution as quickly as possible," said Brizard.