Allocation of the sales and subsequent income is at the top of this heap of nexus mess. States don’t want to unnecessarily complicate things, but they do want money.
Throwback is a common concept but not every state uses it. Again, we’ll pick on California. Under the old rules, when a California business ships TPP to another state, and that business does not have nexus in that state, the sales are “thrown back” to California since it is considered a California sale.
Interestingly enough, there are cases where a sale would not have a tax home at all. Let’s say you sold a service to a customer outside of California. Using the market-based approach and under California’s new rules of bright line nexus (turn back a few pages to review), sales exceeding $500,000 in another state are not thrown back to California. So, if you had sales in another state that did not trigger a filing in that state, these sales could arguably be allocated outside of California but disappear into a black hole. Sounds crazy, but true.
Allocation issues such as these can create tax arbitrage and there are other examples of the same dollar being taxed twice by different states. It truly is a mess. States recognize this growing problem and are working together to eliminate the loopholes. In about three perhaps four hundred years we’ll be good to go.
Taxpayer's Comprehensive Guide to LLCs and S Corps : 2019 Edition