A cut to the tax coal companies pay to fund a trust for sick miners will cost taxpayers at least $15 billion by 2050, according to a new report from a national watchdog group.

An excise tax rate on mined coal that funds the Black Lung Disability Trust Fund expired at the beginning of 2019 due to inaction by Congress. That led to a reduction in the amount coal companies pay into the fund, which pays benefits and medical bills for miners diagnosed with black lung disease.

“By failing to extend the excise tax, Congress is shifting billions of dollars in liabilities from coal companies to taxpayers,” said Autumn Hanna, vice president of Taxpayers for Common Sense. The Washington-based group released a report on Tuesday that said the fund’s debt could be as high as $26 billion by 2050.