I just wanted to post an update. Since the original post I've updated my QuickBooks to the newest version (V. 23) and I also installed the newest Avatax calculator (V. 99). Since the install I have a whole new batch of problems! The New errors are event callback errors. I found a posted fix for that, and it appeared to work. But, the new issue is that Avatax now runs an address validation on every single transaction. I reached out to Avalara and they told me that I needed to simply turn of the validation in the settings. I did that, it still attempts to validate every address. It also locks up both QuickBooks and Avatax upon opening. Everything becomes non-responsive. when I spoke with their tech support, they suggested that maybe my install was bad. I uninstalled / reinstalled, etc. It still won't function. So, I've gutted the module from my users workstations and we are back to using an online calculator for the Nexus map. Has anyone else found something useful out there?