Cook County tax increment financing districts will bring in a record $1.2 billion for the 2018 tax year, according to a report released Wednesday by Cook County Clerk Karen Yarbrough.

A reassessment of Chicago properties is largely the reason the city’s 138 TIF districts generated about $841 million in tax revenue, an $181 million increase from last year.

The reassessment contributed to a 12.5% bump in equalized assessed value, which factored into the 27.4% increase in revenue for the city’s TIF districts.

Tax increment financing districts are used by municipalities to spur economic development in a specific area. Taxes collected on the increase in the property values in the district are used to pay for infrastructure or pay off bonds used to make improvements.

The $1.2 billion is the amount of taxes collected on the increase in the property value of all the TIF districts.

The Red and Purple Line modernization transit TIF generated roughly $116 million, making it the highest grossing TIF and accounting for the majority of the city’s TIF revenue. Many of the districts with the highest revenue are in or around the Loop.

Mayor Lori Lightfoot’s administration said the city is evaluating the TIF report as they begin to balance the city’s books.

“As has been done in years past, we are looking at the full extent of our obligations and evaluating how much is available, and how these funds could be applied to balance several key priorities for the city, which include addressing significant capital needs, reconciling an upcoming deficit in 2020, and ensuring we are maximizing the use of funds to support the continued growth of our schools and neighborhoods,” the mayor’s office said in statement Wednesday.

Former Mayor Rahm Emanuel has used TIF surpluses to supplement the city’s budget. He avoided a Chicago Teachers Union strike in 2016 after using $87.5 million of surplus TIF money to pay for raises in the contract.

The county’s 303 active TIFs span 99 suburban municipalities and are expected to generate about $339 million in tax revenue, a $5 million drop from last year. The report attributes that small decline — about 1.62% — to a slight drop in assessed values of properties.

Yarbrough said she intends to try to continue the work of her predecessor, David Orr, on making sure there’s transparency around the tax financing districts.

“I think [companies and municipalities] use it like a piggy bank,” Yarbrough said about dollars from the financing districts. “If they know the money’s there and they may use it for any number of things. So those of you who live somewhere where there’s a TIF, or if you live in a TIF, you should pay attention to your village fathers and mothers on how the money’s being used.”

Contributing: Fran Spielman