Sales tax is one of the most complex compliance obligations for small business owners. Unlike income tax (which you pay once a year), sales tax must be collected on qualifying transactions, reported, and remitted to state and local governments — often monthly or quarterly. Here's a comprehensive guide for 2026.
What Is Sales Tax Nexus?
Nexus is the connection between your business and a state that triggers a legal obligation to collect and remit that state's sales tax. If you have nexus in a state, you must collect sales tax on taxable sales to customers in that state.
Physical Nexus
You have physical nexus in a state if you have:
- A physical office, store, or warehouse
- Employees who work in or travel through the state
- Inventory stored in a fulfillment center (including Amazon FBA warehouses)
- A sales representative operating in the state
Economic Nexus (Post-Wayfair)
Since the 2018 South Dakota v. Wayfair Supreme Court decision, all 45 sales-tax states have enacted economic nexus laws. These require out-of-state sellers to collect tax if they exceed certain thresholds of sales into that state — typically $100,000 in revenue OR 200 transactions per year. This affects online sellers especially.
How to Register for Sales Tax
Once you determine you have nexus in a state, you must register for a sales tax permit (also called a seller's permit or resale certificate) in that state before you begin collecting tax. Collecting without a permit is illegal in most states. Registration is usually done through the state's Department of Revenue website. Most states charge no fee for registration, though a few charge small fees.
If you have nexus in multiple states, you can use the Streamlined Sales Tax Registration System (SSTRS) to register in up to 24 member states simultaneously through one application.
What Rate Do You Charge?
You charge the combined rate for the customer's delivery address — the "destination-based sourcing" model used by most states. This means:
- A customer in Austin, TX → you charge Austin's combined rate (8.25%)
- A customer in Los Angeles, CA → you charge LA's combined rate (10.25%)
- A customer in Portland, OR → you charge nothing (Oregon has no sales tax)
A few states use "origin-based sourcing" where you charge the rate at your business location rather than the customer's location. These include Texas, Arizona, and a handful of others for in-state sales.
What Products Are Taxable?
Taxability rules vary dramatically by state. Common exemptions include:
- Groceries: Exempt in many states (but not all, and definitions of "grocery" vary)
- Clothing: Exempt in Pennsylvania, New Jersey, New York (under $110), Minnesota
- Prescription drugs: Exempt in all sales-tax states
- Digital goods: Some states tax digital downloads, software, and streaming subscriptions; many don't
- Services: Most states don't tax services, but some do — and the definition of "service" varies
- Resale goods: Items purchased for resale are exempt if the buyer provides a valid resale certificate
Filing and Remitting Sales Tax
Filing frequency depends on your sales volume in each state:
- Monthly: High-volume sellers (thresholds vary by state)
- Quarterly: Medium-volume sellers
- Annually: Low-volume sellers
When you file, you report gross sales, taxable sales, tax collected, and any deductions or credits. You then remit the tax amount owed. Always file on time — late filing penalties and interest can be significant, and some states charge penalties as a percentage of tax owed.
Using Tax Automation Software
For most small businesses selling across multiple states, manual sales tax calculation is impractical. Tax automation platforms like TaxJar, Avalara, or Vertex can automatically calculate the correct rate for every transaction based on the customer's address and product type, and even auto-file returns in each state. The cost is typically $20–$500/month depending on your volume and the number of states.
Common Mistakes to Avoid
- Not registering after crossing an economic nexus threshold — You could face back taxes, interest, and penalties for the entire uncollected period
- Charging the wrong rate — Charging too little means you absorb the difference; charging too much could expose you to customer complaints
- Not accepting valid exemption certificates — If a business customer provides a valid resale certificate, you must not charge them tax
- Missing filing deadlines — Even if you owe zero tax, file on time to avoid penalties in most states
- Ignoring marketplace sales — Even if Amazon or Etsy collects and remits tax for you, those sales still count toward your economic nexus thresholds
Calculating Sales Tax the Right Way
For quick calculations on individual transactions, use our free sales tax calculator. For bookkeeping purposes, if you already have the total amount collected and need to split it into base price and tax for your records, use the reverse calculation tool on our homepage — enter the total and your state's combined rate to get the exact pre-tax amount and tax paid.