US sales tax is a state-level tax that businesses must collect when they have nexus in a state. If you meet physical or economic nexus thresholds, you must register, collect, file, and remit sales tax, failure to do so can result in back taxes, penalties, and interest.
For many businesses, US sales tax can feel confusing due to the number of different state rules and requirements. This guide breaks everything down into simple terms so you can understand how it works and what your responsibilities are.
What Is US Sales Tax?
US sales tax is a consumption tax applied to the sale of goods and certain services, collected by businesses and paid to state and local governments.
Unlike VAT systems:
- There is no federal sales tax
- Each state sets its own rules
- Local jurisdictions may apply additional rates
This means sales tax rules vary significantly depending on where your customers are located.
The most important point to remember is that you must collect US sales tax when your business has nexus in a state, which can be triggered by physical presence or by exceeding economic thresholds.
Once nexus is created:
- You must register
- You must collect tax
- You must file returns
How US Sales Tax Works
US sales tax is charged at the point of sale and collected by the seller on behalf of the state.
In practice, the process looks like this:
- A customer places an order
- Sales tax is calculated based on their location
- The business collects the tax at checkout
- The business reports the sale to the state
- The tax is paid to the state
Think of your business as a tax collector on behalf of the government, not the taxpayer itself.
Origin vs Destination-Based Sales Tax
One of the most misunderstood parts of US sales tax is how rates are determined.
There are two main systems:
- Origin-Based States – Tax is based on the seller’s location.
- Destination-Based States – Tax is based on the customer’s location (most common).
Example: If you sell from Texas to California, you typically charge California rates, not Texas.
This is especially important for ecommerce businesses selling across multiple states.
When Do You Need to Collect Sales Tax?
You need to collect US sales tax when your business creates nexus in a state.
Nexus is the connection that creates a legal obligation.
Types of Nexus
1. Physical Nexus
Physical nexus is created when your business has a physical presence in a state.
Common triggers:
- Inventory stored in warehouses (including Amazon FBA or 3PLs)
- Employees or contractors
- Offices or facilities
Physical nexus creates an immediate obligation.
2. Economic Nexus
Economic nexus is created when your sales exceed a state’s threshold.
Most states use thresholds such as:
- $100,000 in revenue
- $500,000 in larger states
These thresholds apply even if you have no physical presence.
For a deeper breakdown of thresholds and triggers, see our guide on when you need to register for US sales tax.
Step-by-Step: How to Comply with US Sales Tax
Step 1: Determine Where You Have Nexus
- Review sales by state
- Check inventory locations
Step 2: Register for Sales Tax Permits
Register in each state where you have nexus
Step 3: Set Up Tax Collection
- Configure your systems (e.g. Shopify)
- Apply correct rates
Step 4: Collect Sales Tax
Charge customers at checkout
Step 5: File Returns
Monthly, quarterly, or annually
Step 6: Remit Tax
Pay collected tax to the state
For a full operational breakdown, see our sales tax compliance guide for businesses.
Worked Examples
Example 1: Single-State Business
- Based in Texas
- Sells only within Texas
They must:
- Register in Texas
- Collect Texas sales tax
Example 2: Remote Seller
- Based in New York
- $120,000 in Florida sales
Florida threshold = $100,000
They must:
- Register in Florida
- Collect Florida tax
Example 3: Ecommerce Business
- Selling nationwide
- Inventory in multiple states
Likely:
- Physical nexus in inventory states
- Economic nexus in multiple states
Therefore multi-state compliance is required.
Common Sales Tax Mistakes
Many businesses struggle with sales tax because they underestimate how complex it becomes as they grow.
Common issues include:
- Not understanding when nexus is triggered
- Delaying registration after crossing thresholds
- Charging incorrect tax rates
- Missing filing deadlines
- Assuming ecommerce platforms handle everything
These mistakes can lead to significant financial exposure over time.
FAQs
Do all businesses need to collect US sales tax?
No, only those with nexus in a state.
Is US sales tax the same in every state?
No, rules and rates vary by state and locality.
What happens if I don’t collect sales tax?
You may owe back taxes, penalties, and interest.
Do I need to register before collecting tax?
Yes, you must register first.
How often do I need to file?
Depends on the state: monthly, quarterly, or annually.
Final Thoughts
US sales tax can seem complex at first, but it becomes manageable once you understand the core concepts and how they apply to your business.
The key takeaway is sales tax obligations are triggered by nexus, not by choice.
By understanding how US sales tax works, you can:
- Stay compliant
- Avoid costly mistakes
- Scale your business with confidence
If you need help understanding your US sales tax obligations or staying compliant across multiple states, RJM Tax Exemption can guide you through registration, filing, and ongoing compliance.
