US Drop Shipping & State Nexus Thresholds

[sabian1982]

• I have a new ecommerce store that is primarily aimed at the US market (at least for now)
• I've created a UK based Ltd that the ecom brand operates under to ensure no personal liability
• All products are sourced, fulfilled and shipped by drop shipping providers in the US

What do I need to know (and do) about US tax and nexus thresholds?

Is it worth (or important) to get an EIN now? I believe this is free and simply a case of a phone call!

Should I simply keep track of the nexus threshold for each respective State, and when I'm 80-90% of the way to reaching that threshold, then look at registering in the respective state?