Selling online has never been easier, but understanding ecommerce and marketplace sales tax obligations is another story. Between state laws, platform rules, and cross-border transactions, knowing who is responsible for collecting and remitting sales tax can make or break compliance. Mistakes here can cost businesses thousands in penalties or unexpected audits.

This guide breaks down when marketplaces must collect sales tax, when sellers are still responsible, and how buyer location affects obligations, especially for U.S. sellers.

Understanding Ecommerce & Marketplace Sales Tax Obligations

In the United States, sales tax obligations depend on where your customers are, how you sell, and through what platform. Traditionally, sellers collected sales tax directly from buyers. However, as ecommerce grew, states introduced marketplace facilitator laws, shifting much of that responsibility to online platforms.

Marketplace facilitators, like Amazon, eBay, Walmart Marketplace, and Etsy, are now required to collect and remit sales tax on behalf of third-party sellers in most U.S. states. But that doesn’t mean individual sellers are off the hook entirely.

Therefore, every business selling online must understand when the marketplace handles tax and when they must step in.

When Marketplaces Must Collect Sales Tax

Marketplace facilitator laws were introduced to simplify tax collection in the digital economy. Under these rules, large platforms that process payments, listings, and deliveries are treated as “the seller of record” for sales tax purposes.

In most states, this means the marketplace must:

• Collect sales tax at checkout from the buyer.
• Remit that tax to the appropriate state or local tax authority.
• Provide records to both sellers and the government.

For example:

• California, New York, and Texas require marketplaces to handle collection and remittance.
• Florida and Illinois follow similar laws, ensuring sellers on major platforms don’t have to file state-specific returns for those sales.

However, sellers still need to track which states their marketplaces cover, because not all platforms manage every jurisdiction equally.

When Sellers Are Still Responsible

Even with marketplace collection laws, sellers still have their own sales tax obligations.

You may still need to:

• Register for a sales tax permit in states where you meet nexus thresholds.
• Collect tax on non-marketplace sales, such as through your own website.
• File sales tax returns if required by your business model.

For instance, if you sell through both Shopify and Amazon, Amazon may handle marketplace sales, but Shopify transactions remain your responsibility.

Moreover, if you store inventory in fulfillment centers across states, you may trigger physical nexus, a connection requiring tax registration even if your marketplace collects on your behalf.

To stay compliant, sellers must monitor where their products are stored and sold and confirm whether the marketplace has covered their sales tax filing obligations for each state.

The Role of Buyer Location in Marketplace Sales Tax

In ecommerce, buyer location determines where sales tax applies. This concept—called “destination-based tax”—means the state or locality where the buyer receives the product dictates the tax rate.

For example:

• A California buyer purchasing from a New York seller pays California’s rate, not New York’s.
• In some states, local taxes also apply (e.g., city or county-level surcharges).

As a result, both marketplaces and sellers must ensure their platforms calculate the correct destination-based rate. Failing to do so could cause under-collection or overpayment, two major red flags in audits.

Cross-Border Ecommerce Challenges

While this article focuses on U.S. sales, many ecommerce businesses also face cross-border challenges when selling to international customers. Import duties, VAT, and GST add complexity that U.S. sales tax systems don’t.

For example, selling from the U.S. to a customer in Canada or the EU may require the seller to register for foreign tax collection systems. Platforms like Amazon and eBay often manage this for global sellers, but not always.

Therefore, even if your marketplace handles U.S. tax, you may still need to register abroad depending on your sales volume and marketplace agreements.

How IST Simplifies Ecommerce Sales Tax Compliance

Navigating ecommerce and marketplace sales tax obligations across 50 U.S. states can quickly become overwhelming. That’s where IST helps.

Integral Sales Tax (IST) automates every part of the compliance process, from registration to calculation and remittance. Whether you sell through Amazon, Shopify, or your own site, IST ensures the correct rates are applied and the right filings reach each jurisdiction on time.

With IST, you can:

• Automatically track marketplace vs. direct sales.
• Monitor state nexus thresholds.
• Get real-time sales tax calculations for all U.S. states.
• Generate accurate tax returns ready for filing.
• Avoid duplicate filings or overpayments caused by marketplace automation gaps.

As a result, businesses stay compliant while focusing on growth, not paperwork.

Final Words

Ecommerce has transformed how small businesses sell, but it’s also changed who is responsible for sales tax. Knowing when the marketplace collects versus when you must file ensures compliance and protects your business from fines.

Even with marketplace facilitator laws, sellers should continue tracking nexus, monitoring inventory locations, and keeping accurate tax records. With IST, you can automate these steps and ensure you never miss a filing again.

Simplify your ecommerce and marketplace sales tax obligations. Get started with IST today.