Assumptions will work with insurance companies, *if* the doctors records match up what you fill. 0If they don't, then expect charge backs. And yes, ins companies can do charges back for filling "incomplete" prescriptions such as for "metoprolol" when the tartrate vs succinate is not specified. In reality, they are going to be looking at big ticket items and aren't going to pay their adjuster to be going through auditing metoprolol scripts. I have seen chargebacks when an insulin pen was dispensed instead of vials on an unclear script.
I have never had an issue... Not to say that it may not be one, but if it is, you're probably out a few dollars. I'm not going to let that bother me. There are more serious chargebacks such as incorrect day supply....and such.