This is not current, but somewhere to start. https://www.caltax.com/spidellweb/public/webinars/webinar-materials/MarijuanaCPE.pdf

https://caltaxminute.com/taking-on-clients-in-the-marijuana-industry-too-risky

More recent https://www.wolterskluwer.com/en/expert-insights/california-provides-tax-credits-for-cannabis-busine...

P.S. We all have the right to refuse service to those who have tax issues we are not comfortable to work with. I knew I was comfortable in this profession when I fired my first customer and then definitely comfortable when I sent one "down the street" to find someone that could handle this return.