![The Ultimate Guide to Multistate Taxation in California — What Is Nexus? [Definition + Examples]](https://sambrotman.com/wp-content/uploads/2025/12/7O1A9789-scaled.jpg.webp)
Quick Answer
Nexus is the connection between a business and a state that creates a tax filing obligation. Four categories: (1) physical presence nexus — property, employees, inventory; (2) economic nexus — sales threshold ($500K CA post-Wayfair); (3) affiliate / click-through nexus; and (4) marketplace facilitator nexus. The short version is that nexus rules expanded dramatically after South Dakota v. Wayfair (2018). In our experience, most multistate compliance problems stem from not recognizing economic nexus thresholds.1
Nexus question? A 15-minute consultation is free.
Nexus — Legal Definition
Nexus (noun, from Latin: "connection") — in tax law, the legally sufficient connection between a business and a taxing state that gives that state the constitutional authority to impose tax obligations. The U.S. Supreme Court established the modern nexus framework in Complete Auto Transit v. Brady (1977) and expanded it in South Dakota v. Wayfair (2018), which authorized states to impose sales tax obligations on businesses with purely economic connections — no physical presence required. In California, nexus is administered separately by the CDTFA (sales and use tax) and the FTB (income and franchise tax), each with distinct thresholds and tests.
Four categories of state tax nexus.
If California is asserting nexus for your business — or you’re uncertain whether your out-of-state activity creates California tax exposure:
California nexus rules are aggressive and extend to economic presence, not just physical presence. A free 15-minute call covers whether your business activities trigger California income or sales tax nexus, what the FTB or CDTFA can actually audit, and what a clean nexus analysis looks like.
Talk to Sam — Free 15-Minute Call → Or call: (619) 378-3138
The Four Nexus Categories
| Category | Trigger2 |
|---|---|
| Physical | Property, employees, inventory |
| Economic | $500K CA / varies by state |
| Affiliate | In-state affiliate relationships |
| Marketplace | Marketplace sales through facilitator |
Quick Reference
Jump to: physical, economic, affiliate, or marketplace.
1. Physical Presence Nexus
Property, employees, inventory, or offices in state.
If this is you: Office, warehouse, employees, or inventory in state. Creates nexus per Quill (physical presence) and continues post-Wayfair as one path to nexus.
Physical Nexus Strategy
- Inventory all states where present.
- Identify property / employees.
- Evaluate FBA inventory in states.
- Register where required.
- File returns in nexus states.
2. Economic Nexus
Post-Wayfair sales thresholds create nexus without physical presence.
If this is you: Online seller exceeding state thresholds. CA: $500K. Many states $100K or 200 transactions. Each state's threshold applies independently.
3. Affiliate / Click-Through Nexus
In-state affiliates or click-through arrangements.
If this is you: Affiliate marketers in state or click-through arrangements with in-state publishers. Some states assert nexus; many overlap with economic.
4. Marketplace Facilitator Nexus
Amazon, eBay, Etsy collect and remit as facilitators.
If this is you: Marketplace seller. Facilitator handles state sales tax. Your direct sales outside marketplace still create nexus where applicable.
Nexus question? Book consultation.
Nexus Authority Lookup
| Authority | Purpose |
|---|---|
| Wayfair (2018) | Economic nexus permission |
| Quill (1992) | Prior physical-presence rule |
| CA RTC §6203 | CA retailer definition |
| PL 86-272 | Income tax solicitation-only protection |
| MTC compact | Uniform state guidance |
Nexus Statute
- 3-year standard, 4-year CA FTB.
- Unfiled returns: unlimited statute.
- Voluntary disclosure can limit look-back.
Nexus Patterns
| Situation | Outcome |
|---|---|
| Physical + unregistered | Retroactive tax + penalty |
| Economic threshold crossed | Register prospectively |
| Marketplace only | Often low obligation |
| Voluntary disclosure | Limited look-back |
Nexus Audit Escalation
Examination
Activity review in state.
Assessment
Back tax + penalty.
Appeal
Factual challenge.
First 48 Hours
- Inventory activities by state.
- Identify nexus states.
- Evaluate registration needs.
- Consider voluntary disclosure.
- Engage counsel.
The ROI Question
Retroactive multistate exposure reaches six figures. Proactive nexus analysis prevents catastrophic back-tax.
When to Engage
- Multi-state business.
- E-commerce / online seller.
- Retroactive tax notice.
- Voluntary disclosure consideration.
Frequently Asked Questions
What is nexus?
Connection between business and state creating tax filing obligation. Four categories: physical, economic, affiliate / click-through, marketplace facilitator. Each state applies its own rules.
What changed with Wayfair?
Supreme Court 2018 overruled Quill's physical presence requirement for sales tax. States can impose economic nexus based on sales thresholds. Expanded state taxing authority dramatically.
What is CA economic nexus?
$500K annual sales into CA. Post-Wayfair threshold. Creates sales tax and potentially income tax registration obligation. Threshold measured annually.
What is PL 86-272?
Federal law protecting out-of-state sellers from state income tax where activity is limited to solicitation of orders for tangible personal property approved and shipped from outside state. Protection narrower than commonly believed.
Does Amazon FBA create nexus?
Inventory in Amazon warehouses in states can create physical nexus. Marketplace facilitator laws may shift tax collection to Amazon, but nexus still exists for income tax purposes in some states.
What's marketplace facilitator law?
State laws requiring marketplaces (Amazon, eBay, Etsy) to collect and remit sales tax on third-party seller transactions. Shifts sales tax obligation from seller to facilitator.
Do I register in every state?
Only nexus states. Nexus analysis determines where. Registration creates ongoing compliance obligations. Evaluate before registering.
What is voluntary disclosure?
State programs permitting pre-contact disclosure of past non-compliance. Limited look-back period (typically 3-4 years). Reduced penalties. State-specific procedures.
Does telecommuter employee create nexus?
Often yes. Remote employee working from their state typically creates employer nexus. COVID-era temporary relief mostly expired.
Does attending trade show create nexus?
Many states have limited protections. De minimis activity thresholds. Some states impose income tax nexus for limited activities.
What's click-through nexus?
Relationship with in-state publishers generating referrals. Pre-Wayfair state response to online sales. Less relevant post-Wayfair but still on books.
How do states find out?
Marketplace facilitator reporting, 1099-K data sharing, state-to-state information sharing, customer complaints, competitive tips. Detection increasingly automated.
What if I'm over threshold unknowingly?
Voluntary disclosure before contact is optimal. Limits look-back. Reduces penalties. Many states have structured programs.
Next Steps
Nexus question? 15-min consultation free.
Need help working through your nexus exposure? We handle multi-state nexus disputes and voluntary disclosures across all 50 states — most often after a marketplace facilitator notice or a state inquiry letter. Book a free 15-minute call to walk through your specific situation.