Sales Tax Nexus: What Retailers Need to Know

Understanding your obligations across states before the IRS (or state) comes calling.

If you sell products or services across state lines — whether through an online store, physical location, or third-party platform — sales tax nexus is a term you cannot afford to ignore.

The landscape of sales tax changed drastically after the South Dakota v. Wayfair Supreme Court decision in 2018, and since then, the rules have only grown more complex. For retail businesses, e-commerce sellers, and even service providers, knowing where and when you owe sales tax can make or break compliance.

At Shah & Trivedi CPA, PLLC, we help businesses simplify these complexities — making multi-state compliance less about confusion and more about clarity. Here’s everything you need to know about sales tax nexus, why it matters, and how to manage it effectively.

What Exactly Is Sales Tax Nexus?

“Nexus” simply means a connection — a link between your business and a particular state that gives that state the right to require you to collect and remit sales tax.

Historically, this connection was based on physical presence — like having an office, store, or employee in the state. But in today’s digital economy, economic nexus has taken center stage, meaning even online retailers with no physical footprint may still owe taxes based on sales volume.

In short:

• Physical Nexus = Presence-based connection
• Economic Nexus = Sales or transaction-based connection

Both can apply simultaneously, and every state sets its own thresholds.

Types of Nexus That May Affect You

Let’s break down the five most common ways businesses establish sales tax nexus in the U.S.:

1. Physical Nexus

   You create physical nexus if you:

   • Maintain an office, warehouse, or retail store
   • Have employees or contractors working in the state
   • Store inventory (even if through a fulfillment service like Amazon FBA)
   • Attend trade shows or conduct temporary sales

   Even a single employee or booth at an event can trigger nexus under some state laws.

2. Economic Nexus

   This is the most common trigger for online sellers. States have thresholds based on sales revenue or transaction count.

   For example:

   • California: $500,000 in annual sales
   • Texas: $500,000 in annual sales
   • New York: $500,000 and 100 or more transactions
   • South Dakota: $100,000 or 200 transactions

   If you exceed these limits, you must collect and remit sales tax, even without physical presence.

3. Affiliate Nexus

   If you have relationships with in-state affiliates or third parties that help you sell, you may create nexus through them.

   Example: If a blogger in Florida promotes your products and earns a commission on each sale, you might have nexus there.

4. Click-Through Nexus

   Some states have “click-through” laws — if you generate a certain amount of revenue through online referrals from local websites or influencers, you’re considered to have nexus in that state.

5. Marketplace Nexus

   Selling on platforms like Amazon, eBay, Etsy, or Walmart Marketplace adds another layer. In most states, the marketplace facilitator (like Amazon) is required to collect and remit tax on your behalf — but that doesn’t always exempt you from registration or filing requirements.

How to Know Where You Have Nexus

Tracking nexus isn’t a one-time task. It’s an ongoing process, especially if your business grows or expands into new regions.

Here’s how to evaluate your exposure:

Step 1: Review Sales Data by State

Run a report showing gross sales and transaction counts by state for the current and prior years. Compare these to each state’s economic nexus thresholds (available on state websites or through your CPA).

Step 2: Identify Physical Touchpoints

List all locations where you store inventory, employ workers, or attend trade shows. Even temporary activity can count.

Step 3: Track Third-Party Sales Channels

If you sell through Amazon, Shopify, or other marketplaces, verify which states the platform collects and remits taxes — and where you remain responsible.

Step 4: Maintain Updated Documentation

Keep records of:

• Invoices and receipts
• Marketplace reports
• Tax exemption certificates (for resale customers)
• State registration confirmations

This makes compliance smoother during audits or reviews.

Why Nexus Compliance Matters

Ignoring nexus obligations doesn’t just lead to a few penalties — it can compound into serious financial risk.

Penalties and Interest

States impose fines, back taxes, and interest for each period of noncompliance — often going back three to seven years.

Personal Liability

In some states, business owners and officers can be held personally responsible for unpaid sales taxes.

Business Disruption

Sales tax noncompliance can delay M&A deals, financing, or state licensing renewals. Lenders and investors frequently review tax records during due diligence.

Being proactive ensures that your business remains in good standing and audit-ready.

How to Register and Comply in New States

Once you determine you have nexus, the next steps are to register, collect, and remit properly.

1. Register for a Sales Tax Permit

   Each state requires separate registration, usually through the Department of Revenue. Some allow centralized filing through the Streamlined Sales Tax (SST) Program, which simplifies registration in 24 member states.

2. Collect the Correct Tax Rate

   Sales tax isn’t just state-based — local jurisdictions (counties and cities) can impose their own rates. The combined rate often varies by ZIP code.

   Cloud-based POS or e-commerce systems (like Shopify or QuickBooks Commerce) can automate rate calculation.

3. Remit and File on Schedule

   Filing frequency (monthly, quarterly, or annually) depends on your sales volume. Missing deadlines can result in automatic late fees.

4. Keep Records Organized

   Store all reports and exemption certificates for at least four years, as most state audit windows fall within this timeframe.

Common Sales Tax Mistakes Retailers Make

Even well-run businesses stumble on sales tax compliance. Here are the most common pitfalls to avoid:

1. Assuming Online Sales Are Exempt

   Many retailers still believe online sales escape state taxes — not true. Economic nexus laws apply to remote sellers, not just in-state ones.

2. Ignoring Small-State Thresholds

   Some states (like Kansas or Florida) have no transaction threshold, meaning any sale may trigger obligations.

3. Not Tracking Fulfillment Inventory

   If you use Amazon FBA, your inventory may move across state lines without your knowledge. Each location can create nexus.

4. Failing to Update Software

   Tax rates and thresholds change frequently. Outdated accounting software can miscalculate taxes and cause under-collection.

5. Forgetting About Exemption Certificates

   If you sell to resellers, you must collect valid resale certificates. Missing or expired certificates can make you liable for uncollected tax.

Multi-State Businesses: Simplify with CPA Oversight

Operating in multiple states can feel overwhelming, but compliance doesn’t have to mean complexity. A CPA can manage your entire multi-state sales tax lifecycle:

• Nexus analysis — Determine where obligations exist
• Registration management — Handle state applications and renewals
• Automated filings — File accurately and on time
• Audit support — Respond to state notices or reviews
• Sales tax integration — Connect your accounting and e-commerce systems

At Shah & Trivedi CPA, we help businesses stay ahead of shifting state tax laws — so you can focus on sales, not spreadsheets.

What to Do If You’re Out of Compliance

If you discover that you’ve been selling into a state without collecting tax, don’t panic — but don’t ignore it either. States often offer Voluntary Disclosure Agreements (VDAs) that allow you to come forward, pay past due taxes, and reduce or eliminate penalties.

Here’s the process:

1. Contact your CPA for a nexus study and exposure analysis.
2. Determine whether a VDA or retroactive registration makes sense.
3. File all past-due returns and set up future compliance.

Acting early demonstrates good faith — and can prevent far harsher enforcement later.

Key Takeaways

• Sales tax nexus defines your obligation to collect and remit taxes in a state.
• Both physical presence and economic activity can create nexus.
• Every state has unique thresholds, rates, and filing rules.
• Automating compliance through proper software and CPA oversight saves time and risk.
• Voluntary disclosure programs can help fix past mistakes with minimal penalties.