US Sales Tax for Ecommerce Sellers: A Complete Guide for 2026

US sales tax is one of the most confusing topics for ecommerce sellers - especially for non-residents and those selling across multiple states. Unlike many countries with a single national tax, the US has thousands of tax jurisdictions with different rules. This guide breaks down what you need to know to stay compliant in 2026.

How US Sales Tax Works

Sales tax in the US is charged at the state and local level, not the federal level. Each state sets its own rate and rules, and counties and cities can add their own local rates on top. This means the tax a customer pays can vary significantly depending on where they live.

Understanding Economic Nexus

Nexus is the connection between your business and a state that requires you to collect and remit sales tax there. There are two main types:

• Physical nexus: Having a physical presence such as an office, employees, or inventory stored in a state (including inventory in Amazon FBA warehouses).
• Economic nexus: Exceeding a state's sales threshold - commonly $100,000 in sales or 200 transactions per year, though thresholds vary by state.

Once you cross a nexus threshold in a state, you are generally required to register, collect, and remit sales tax there.

Marketplace Facilitator Laws

Here is good news for many sellers: most US states have marketplace facilitator laws. These require marketplaces like Amazon and Walmart to collect and remit sales tax on behalf of their sellers. If you sell only through these marketplaces, they typically handle sales tax collection for you in most states.

However, you may still have registration or reporting obligations, and if you sell through your own website (for example, Shopify), you are responsible for collecting tax yourself once you have nexus.

Step 1: Determine Where You Have Nexus

Review where your inventory is stored, where your sales volume is highest, and which state thresholds you have crossed. FBA sellers should pay special attention because Amazon may store inventory in many states.

Step 2: Register for Sales Tax Permits

Where you have nexus and an obligation, register for a sales tax permit with that state's Department of Revenue before collecting tax. Collecting tax without a permit is not allowed.

Step 3: Collect the Right Amount

If you sell through your own store, configure your platform to charge the correct combined state and local rate based on the customer's location. Marketplaces handle this automatically for marketplace sales.

Step 4: File and Remit Returns

File sales tax returns on the schedule each state assigns (monthly, quarterly, or annually) and remit what you collected. File on time even if you owe nothing, since missing a zero return can still trigger penalties.

Tips to Stay Compliant

• Use sales tax automation software to track nexus and calculate rates.
• Keep clear records of where your inventory is stored.
• Do not ignore states just because a marketplace collects for you - confirm your registration obligations.
• Consult a US sales tax professional when in doubt.

Conclusion

US sales tax is complex, but manageable once you understand nexus, marketplace facilitator laws, and your filing obligations. The key is knowing where you have nexus and staying registered and compliant in those states. If you want expert help setting up your US business and navigating sales tax compliance, our team can guide you through every step.