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Practical guide

How to Calculate Sales Tax for Online Sellers

A plain-English guide to sales tax for online sellers: nexus rules, marketplace facilitator laws, how to calculate tax on orders, and which states have no sales tax.

By CalcBusiness editorial team · Reviewed 2026-07-15 · About our team

Formula and assumptions

Sales tax = sale price × tax rate

Tax-inclusive price: sale price = total ÷ (1 + rate)

Taxability, sourcing, nexus thresholds, and measurement periods are jurisdiction-specific.

How it works

  1. Identify physical connections and review each state's current remote-seller threshold, measurement period, and included sales.
  2. Separate direct-store orders from orders actually completed through a marketplace facilitator; the reporting treatment can differ by state.
  3. Confirm product taxability and the state's sourcing rule before using an address-level combined rate.
Use the Sales Tax Calculator →

Frequently asked questions

Do I need to collect sales tax for online sales?

It depends on your connection to the state, the state's current remote-seller rule, what you sell, and the sales channel. Threshold amounts, included sales, lookback periods, and registration timing differ. Check the destination state's revenue department before collecting.

What is economic nexus?

Economic nexus is a state-law test that can create a collection obligation for a remote seller based on sales activity without physical presence. It is not one national $100,000-or-200-transaction rule: states use different amounts, sales bases, periods, and effective dates, and many have removed transaction-count tests.

Do I need to collect sales tax if I sell on Etsy or Amazon?

A marketplace may collect and remit tax for an order when state law treats it as the facilitator, but that does not eliminate every seller registration, reporting, or nexus obligation. Shopify Payments is a payment service, not proof that a direct Shopify-store order is a marketplace sale. Shopify says merchants decide where to collect on direct-store transactions; qualifying Shop-channel orders can be treated separately.

Which states have no sales tax?

Five states have no state sales tax: Alaska, Delaware, Montana, New Hampshire, and Oregon. However, Alaska allows local municipalities to impose sales taxes.

Is sales tax based on where I am or where my customer is?

Often the delivery destination matters for interstate remote sales, but sourcing can depend on the state, seller facts, product, and order. Do not use a statewide rate or this calculator as an address-level tax engine.

Limitations: Sales tax rules change frequently and vary by state and product type. This guide is for general education only. Consult a tax professional or CPA for your specific situation.

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Sales Tax Basics for Online Sellers

Sales tax is a consumption tax imposed by state and local governments on the sale of goods and some services. As an online seller, you may be required to collect sales tax from buyers in states where you have "nexus" — a legal connection that triggers tax obligations.

What Is Nexus?

Nexus comes in two forms:

  • Physical presence: Offices, employees, inventory, warehouses, events, or other in-state activity can matter. Inventory in a fulfillment network requires state-specific review; this guide cannot infer where inventory is stored or whether an exception applies.
  • Economic nexus: A state can impose a remote-seller collection duty when its own sales-activity test is met. The monetary amount, transaction test, sales included, lookback period, and effective date are not uniform.

Check the current rule state by state

There is no safe “most states” shortcut. For example, the current Streamlined Sales Tax state table shows different monetary thresholds, states without transaction thresholds, and different definitions of the sales counted. Use its links to the destination state's revenue department, then preserve the dated source used for your decision. See the Remote Seller State Guidance.

Marketplace Facilitator Laws

A platform may collect and remit for an order that is legally a marketplace-facilitated sale. That treatment is order- and jurisdiction-specific; it does not automatically eliminate registration, informational filing, or nexus tracking by the seller.

Confirm the marketplace status in the order report and the state's instructions. In particular:

  • Do not collect the same tax twice when the order record confirms that a facilitator collected it.
  • Do not assume every order associated with a brand or payment method received marketplace treatment.
  • Some states still require marketplace sales to appear in gross or exempt-sales reporting.

Shopify distinction:Shopify Payments processing does not by itself turn a direct Shopify-store order into a marketplace sale. Shopify states that merchants choose where to collect tax on direct-store transactions. Orders completed through the Shop sales channel can receive separate marketplace treatment. Review Shopify's US sales-tax guidance and Shop-channel tax guidance.

How to Calculate Sales Tax on an Order

The delivery address often affects a remote order, but state sourcing and product-taxability rules determine the actual rate and tax base. Use the Sales Tax Calculator to look up the rate for any US state and calculate the tax on any sale amount.

Arithmetic example only: if an address-level tax engine returns a combined 9.5% rate for a taxable $50 item:

  • At 9.5% total: $50 × 9.5% = $4.75 tax
  • Customer total: $50 + $4.75 = $54.75
  • The example does not assert that 9.5% applies to a particular address or product.

Steps to Get Sales Tax Compliant

  1. Map physical connections. Record offices, people, inventory, fulfillment locations, and other in-state activity for professional review.
  2. Run state-specific threshold reports. Use the exact sales base and measurement period in each current state rule; do not apply one national threshold.
  3. Separate channels. Retain direct-store, marketplace-facilitated, exempt, resale, refunded, and taxable sales as distinct report lines.
  4. Confirm registration timing. Follow the destination revenue department's permit and collection instructions before enabling tax collection.
  5. Configure and reconcile. Test taxability, sourcing, exemptions, and address rates, then reconcile collected amounts, facilitator reports, returns, and payments.

Common Sales Tax Mistakes Online Sellers Make

Most sales tax problems for online sellers come from a handful of recurring mistakes, not from unusual edge cases:

  • Collecting before confirming registration. Permit and collection timing rules differ. Follow the destination revenue department's instructions instead of assuming that collecting first and registering later is acceptable.
  • Using a statewide rate as an address rate. Local jurisdictions, sourcing, product taxability, exemptions, and shipping treatment can change the result. The calculator provides arithmetic, not an address-level determination.
  • Double-collecting on marketplace sales. If Etsy or Amazon already collects and remits tax on an order as a marketplace facilitator, you don't need to collect it again on the same sale through your own records.
  • Using one measurement window everywhere. States can use current year, prior year, calendar periods, or rolling periods and can count gross, retail, or taxable sales differently.
  • Not separating direct and facilitator orders. Both can matter for nexus or reporting even when the facilitator remits the tax. Classify each channel from its actual order records instead of assuming all Shopify or all marketplace-branded orders receive the same treatment.

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