Any #tax #TaxLaw #IRS experts, attorneys, #CPAs here who can answer a question *definitively*, i.e. by citing the IRS' rules about when a #W9 form is needed?

My day job is running a licensed cannabis nursery in NorCal (Plant Humboldt). We sell starter plants to farms and personal use growers. We mostly grow from seed, but sometimes buy rooted cuttings to grow out from other licensed nurseries. We keep getting requests from them for W9s, which IRS says we don't need (best as I can tell and according to the IRS person on the phone). We are not dealing in cash and there are no 8300 forms involved. It's all checks, credit card payments or direct bank to bank wire transfers. There is no logical reason why a W9 is necessary.

On an FB legal weed business forum, everyone insists that getting a #W9form is "normal*, but no one can say where it says required. The ones who say it's required also can't show me where it says that.