My experience is that you reach Nexus before needing to register. Usually that means reaching over 100k in sales or exceeding 100 transactions. It does vary by state. You do register in each state and the rate for collection varies not only by state but by local jurisdictions. Rates vary by state, county, city and special jurisdictions and sometimes on shipping as well. It can be extremely frustrating. Shopify does have tax rate services and reporting that is helpful but lacking. Once you reach nexus and begin collecting, you register in that state and you will learn during registration if you are required to file monthly quarterly, or annually. Failure to file leads to stiff penalties and failure to pay on time brings penalties and interest.
Feel free to contact me if you’d like to be in contact with services that can help with filing.
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