Because we are part of a CPA firm, we received numerous documents and opinions on the South Dakota v. Wayfair, Inc. ruling in favor of South Dakota. There are 21 other states that have laws that also consider ""economic nexus"" (vs. physical nexus), so this is just a beginning. I would imagine the remaining 24 states (4 charge no sales tax) will also be interested in this. My plan is not to scare the customers, but to point out if they are shipping to many states, they need to consider the implications. My opinion is that for those customers, they should seriously consider something like Avalara to automate this process. One key item the CPA on the call stressed is that Exemption Documentation will become very important. Of course, that is another Avalara option - tracking those.