At this time, what is the most notable Accounting challenge for cannabis companies?

The biggest challenge is understanding what can and cannot be deducted on a federal tax return - as well as understanding WHEN those deductions can be taken - due to the severe limitations placed on cannabis companies by IRC 280E.  Very simply, this code section limits deductions to production-related expenses for cannabis growers and cannabis processors and it limits deductions to acquisition-relted expenses for cannabisretailers.

Every business decision - entity structure, fixed asset purchases, product/service mix in a store - all need to be filtered through the lens of IRC 280E.  It can be planned for and managed, but it creates odd twists to most 'normal' financial decisions a business would make.  The reason it needs to be understood well is because it can create a very large chasm between book income and taxable income, necessitating careful tax planning and tax saving throughout the year.