US Sales Tax Nexus for Online Sellers: A Plain-English Guide

Sales tax nexus for online sellers is the connection between a business and a state that may create an obligation to register, collect tax, file returns, and remit the amount collected. A Shopify or Amazon business can create nexus even without an office in the customer’s state.

The difficult part is that sales tax rules are state-specific. Thresholds, measurement periods, taxable products, local rates, filing frequency, and marketplace treatment can differ. This guide explains the bookkeeping and decision process without pretending one rule applies everywhere.

What creates sales tax nexus?

Physical nexus

Physical presence may include an office, store, employee, contractor activity, warehouse inventory, trade-show activity, or other in-state operations. Inventory held by a fulfillment provider can matter even when you do not control the warehouse location.

Streamlined Sales Tax notes that a seller with physical presence is generally not treated as a remote seller and may need to register regardless of remote-seller sales thresholds. Review each state’s guidance for the exact rule.

Economic nexus

Economic nexus is based on sales activity into a state. After the U.S. Supreme Court’s South Dakota v. Wayfair decision, states may require qualifying remote sellers to collect sales tax without a traditional physical presence.

Many states use a $100,000 sales threshold, but this is not universal. Some measure gross sales, some taxable sales, some retail sales, and some retain a transaction-count test. Measurement periods also vary. For example, the Streamlined Sales Tax state tables show different rules across New York, Ohio, Pennsylvania, South Dakota, Virginia, and other states.

Do not apply one state’s threshold to the entire country. Maintain a current state-by-state matrix or use a qualified sales-tax provider.

How marketplace facilitator laws affect Amazon sellers

Marketplace facilitator laws generally require qualifying platforms—such as Amazon or another marketplace—to calculate, collect, and remit tax on facilitated sales. That does not automatically eliminate every obligation for the seller.

You may still need to:

• Include marketplace sales when testing a state’s economic threshold.
• Register or file zero or informational returns in certain states.
• Handle tax on sales made through your own Shopify, WooCommerce, wholesale, or other direct channel.
• Confirm whether the marketplace collected the correct tax on all facilitated transactions.
• Track physical nexus created by inventory, employees, or other activity.

Marketplace rules and seller-registration requirements vary. Streamlined Sales Tax publishes separate guidance for marketplace facilitators and marketplace sellers, but the state revenue department remains the controlling source.

A practical nexus review for Shopify and Amazon sellers

1. Map every place the business operates

List offices, employees, contractors, stores, warehouses, third-party logistics providers, marketplace inventory, and regular in-state activities. This identifies potential physical nexus before you review sales thresholds.

2. Export sales by state and channel

Combine Shopify, Amazon, other marketplaces, wholesale, and offline sales. Preserve gross sales, returns, exempt sales, taxable sales, order count, and destination state. Do not test only the net deposits shown in the bank.

3. Separate marketplace and direct sales

Marketplace-collected tax and direct-channel tax have different operational treatment. Keep both in your nexus analysis because state threshold rules may include marketplace sales even when the marketplace remits the tax.

4. Compare activity with each state’s current rule

Document the threshold basis, measurement period, effective date, sales included, transaction-count requirement, and source link. Review states where you are near the threshold more frequently.

5. Confirm product and customer taxability

Nexus tells you where an obligation may exist; taxability determines what is taxed. Clothing, food, digital products, software, supplements, shipping, and services can receive different treatment. Resale and other exempt sales require valid documentation.

6. Register before collecting

Do not collect a state’s tax until the business is properly registered. Once registered, calendar every filing deadline—even for a period with no taxable sales if the state requires a zero return.

7. Configure the commerce platform and validate results

Set registrations, product categories, locations, and shipping treatment in Shopify, Amazon, or the tax engine. Test sample orders and reconcile tax reports to the sales-tax liability account every filing period.

Bookkeeping entries for sales tax

Sales tax collected from customers is generally a liability, not revenue. A simplified sale may record cash or processor receivable for the total charged, credit sales for the pre-tax amount, and credit sales-tax payable for the tax. When the state is paid, reduce the liability.

Marketplace-facilitated tax may never reach your bank. The settlement accounting must still distinguish product revenue, marketplace fees, refunds, and taxes so gross sales and liabilities are not distorted.

Common sales-tax mistakes

• Assuming every state uses a $100,000 or 200-transaction threshold.
• Ignoring inventory stored by Amazon FBA or a third-party warehouse.
• Testing only Shopify sales and excluding marketplace or wholesale channels.
• Treating all marketplace sales as exempt from nexus analysis.
• Collecting tax before registration.
• Using deposits instead of destination-level gross sales data.
• Recording tax collected as revenue.
• Missing zero returns after registration.

Frequently asked questions

Does Shopify collect and remit sales tax for me?

Shopify provides tax-calculation tools, but a direct seller generally remains responsible for determining registrations, configuration, returns, and remittance. Confirm the services included in your Shopify plan and any connected tax product.

If Amazon collects tax, do I still have nexus?

Possibly. Marketplace collection does not erase physical presence, and some state thresholds include marketplace sales. Registration or filing obligations can remain depending on the state and your other channels.

How often should an online seller review nexus?

At least quarterly for a growing multi-state business, and monthly when sales approach thresholds or inventory and operations change frequently.

Build sales-tax-ready books

Accurate compliance starts with channel-level sales, destination data, marketplace separation, reconciled payouts, and a clean sales-tax liability. AccoTiva’s e-commerce accounting service helps U.S. sellers maintain sales-tax-ready records and monitor the financial data used in nexus reviews.

Request a free bookkeeping and nexus-data review for your Shopify, Amazon, and direct-channel records.

Sources: Streamlined Sales Tax remote-seller guidance, state threshold tables, and marketplace facilitator guidance. This article is general information, not tax or legal advice. State rules change; verify the current requirements with the relevant state or a qualified sales-tax professional.