Six guides covering what changed in 2018, how to tell where you owe, and the specific gotchas for Shopify and Amazon FBA sellers. General information, not tax advice — each guide points you to where to verify the details.
Updated 10 July 2026.
The core concepts, in the order that makes sense to read them.
The 2018 South Dakota v. Wayfair decision let states tax remote sellers on sales volume alone, not just physical presence. Here's what changed, and how state thresholds work.
Read the guideA five-step way to check where you actually owe, instead of guessing — physical nexus, economic thresholds, marketplace coverage, and what comes next.
Read the guideShopify Tax calculates rates at checkout — it doesn't tell you where you have nexus, register you, or file most of your returns. Here's the real division of labor.
Read the guideFBA inventory sitting in a warehouse can create physical nexus on its own. Amazon collects on its sales, but registration and non-Amazon exposure can still be yours.
Read the guideAmazon, Etsy, and Walmart now collect tax on marketplace sales in every state that has one. What that covers, and what it still leaves on the seller.
Read the guideWhat to have ready, what it typically costs (usually free or a small fee), how long it takes, and why you should never collect before you're registered.
Read the guideNo signup required for any of these.