Medical marijuana retailers will soon have to pay some hefty taxes.

The IRS has ruled that dispensaries cannot  deduct standard operating expenses like rent and payroll.  

That could mean an effective federal income tax rate as high as 75 percent.

The IRS said it is enforcing a 1982 law that was aimed at illegal drug dealers.

Agency officials said Congress should change the law if lawmakers don't want medical marijuana dealers to pay the price.

Medical marijuana is now sold in 18 states.