Knowledge Base Avatax WebUI WebUI Upgrade WebUI. Service Layer Internal Error WebUI IIS Configuration Add-On. Settings ShipTo Address from Custom UDFs Display General Add-On. CertCapture Override Certificate Functionalities Set Up Basics Add-On. Functionalities Address Validation Avatax Event Service Running and Monitoring Avatax Event Service Configuration Installation Add-On. Begin How AvaTax Works Connection Setup Lightweight Installation Requirements