Luckily Representative Polis has introduced some legislation to allow medical marijuana centers to deduct business expenses like any other legal business.

Toking And Taxes Don't Mix, Says IRS - Forbes

It's an underhanded attempt at leveraging the marijuana movement out of existence, but in the alternative senario no one would be paying any taxes on any revenue from marijuana being sold on the black-market.

This is a public policy decision and if the IRS code stands will be a major set back for any rational policy for making cannabis medically available in the US.