Wyoming lawmakers are considering simplifying the state's tax code for coal mining companies, a move that some worry could cost the state millions, the Billings Gazette reports.

Mining companies have been forced to spend millions to push further into Wyoming's hills in search of coal, and those increased costs have been taxed as part of the severance rate that coal mining operations incur. State legislators have proposing capping that rate and removing rising mining costs from the tax rate formula.

According to the Gazette, the severance tax on coal brought in $265 million in 2010. State officials estimate the proposed change would cost Wyoming about $16 million over five years. The state's coal taxes would be based strictly on the price of coal and number of tons of coal produced.