Illinois' unpaid bill backlog reached $6.6 billion at the end of the 2015 calendar year, according to a report released Tuesday by Moody's Investors Service.
Moody's report, released a day before Gov. Bruce Rauner's State of the State address, said the state's unpaid bill backlog is growing by about $450 million per month.
The ratings agency warned that the backlog could grow even larger in the coming years.
"If the state fails to address its structural imbalance for subsequent years, the payment backlog will swell to $25 billion, or 64 percent of expenditures, by the end of fiscal 2019," the report says.
Illinois has been operating without a budget for the past six months as Rauner and Democratic leaders remain at odds over a spending plan for the 2016 fiscal year, which began July 1. Illinois has $3.6 billion less in revenue in the current fiscal year as a result of the 2011 temporary income tax sunsetting in January 2015. Even though the state is collecting fewer income tax dollars, a range of programs and services have been funded during the impasse based on 2015 levels because there is no 2016 spending plan in place.
The state's growing bill backlog "is a clear indicator of weak liquidity and governance," Moody's added.
"Growth in the payment backlog is an alternative to politically difficult budget-balancing measures as well as to cash-flow borrowings that can temporarily alleviate liquidity pressures," the report says.
Illinois has a Baa1 rating with a negative outlook from Moody's.