Pot may be illegal in the eyes of the federal government. But the people selling it legally still have to pay their taxes.

Owners of recreational "adult use" marijuana operations in Colorado and Washington are preparing to file their first federal tax returns, and they're learning some hard lessons. The IRS is not allowing all the usual business deductions under what's called section 280E. The cost of growing marijuana is deductible under the federal tax code, but not the cost of selling it.