In 2004, Avalara built AvaTax using SOAP. This has stood the test of time, with thousands of customers still using it every day.
In 2016, Avalara chose to build a completely new REST API that works off the same code and data while also including modern standards. We implemented the OpenAPI specification (also known as Swagger) throughout the API, and we chose to adopt Microsoft’s REST guidelines to make our service immediately familiar to users of the standard.
Whether you have a SOAP or RESTv1 integration, these refactor guides will tell you how to bring your integration up to date with the latest version of the AvaTax APIs.