Free Tax Guide
State Income Tax Considerations in Multistate Tax Planning
Key Takeaway
State income tax on multistate businesses involves four analytical layers: (1) nexus determination for income tax (which can differ from sales tax); (2) PL 86-272 protection for certain out-of-state sellers; (3) apportionment using state formulas — CA uses single-sales factor; and (4) combined reporting rules for unitary businesses. The short version is that state income tax nexus often extends beyond what businesses realize, especially post-Wayfair and with remote workers. In our experience, proper apportionment planning reduces multistate income tax materially.1
State income tax question? A 15-minute consultation is free.
Four layers of multistate income tax.
The Four Income Tax Layers
NexusIncome TaxPL 86-272ProtectionApportionSingle-SalesCombinedUnitary
| Layer | Application2 |
|---|---|
| Income Tax Nexus | Economic + physical |
| PL 86-272 | Solicitation-only protection |
| Apportionment | CA single-sales factor |
| Combined Reporting | Unitary business |
Quick Reference
Jump to: nexus, PL 86-272, apportion, or combined.
1. Income Tax Nexus
Economic nexus extends income tax reach beyond physical presence.
If this is you: Selling into state without physical presence. Economic nexus applies to income tax in many states. Thresholds vary. CA Factor Presence test: $711K sales or $71,154 property/payroll (2024 indexed).
Income Nexus Strategy
- Identify states where sales / activity present.
- Evaluate thresholds.
- Consider PL 86-272 protection.
- Register and file in nexus states.
- Plan apportionment.
2. PL 86-272 Protection
Federal protection for solicitation-only activity in TPP sales.
If this is you: Selling tangible personal property into state. Activity limited to solicitation. Orders approved and shipped from outside state. PL 86-272 protects from income tax. MTC guidance on internet activities narrowing protection.
3. Apportionment — CA Single-Sales Factor
CA apportions multistate income by single sales factor post-2013.
If this is you: Multistate business. CA portion = CA sales / total sales. Service revenue sourced to customer location (market-based). Careful sourcing essential.
4. Combined Reporting
Unitary businesses file combined return for CA.
If this is you: Related entities with unitary operations. CA requires combined reporting. Water’s-edge election available. Worldwide combination default absent election.
State income tax question? Book consultation.
State Income Document Lookup
| Form | Purpose |
|---|---|
| Form 100 | CA corporation return |
| Form 565 | CA partnership return |
| Form 568 | CA LLC return |
| Schedule R | CA apportionment |
| CA Form 100W | Water’s-edge election |
| PL 86-272 | Federal protection |
State Income Statute
- CA: 4-year FTB statute.
- 6-year for 25%+ omissions.
- Unfiled: unlimited.
State Income Patterns
| Situation | Outcome |
|---|---|
| PL 86-272 protected | No income tax |
| Economic nexus + TPP | Protected if applicable |
| Service / digital goods | No PL 86-272 protection |
| Proper single-sales apportionment | Defensible |
State Income Audit Escalation
Examination
Nexus, apportionment, combined reporting review.
Appeals
Factor-specific disputes.
OTA / Court
Formal challenge.
First 48 Hours
- Identify state activities.
- Evaluate nexus.
- Assess PL 86-272 protection.
- Plan apportionment.
- Engage counsel.
★Brotman Law handles state income tax planning. Based in San Diego.
The ROI Question
Proper apportionment saves tens of thousands. Professional planning pays for itself year one.
Dealing with Multistate Tax Exposure?
Multistate obligations don’t announce themselves — most businesses accumulate sales tax, income tax, or payroll tax exposure in other states without realizing it until they’re contacted or audited. If you’re selling across state lines, have remote employees, or aren’t sure where your business has nexus, a brief review can identify where you have exposure and what to do about it.
Review My Multistate Exposure → Or call: (619) 378-3138
When to Engage
- Multistate business.
- Nexus questions.
- Apportionment planning.
- Combined reporting.
State income tax question?
15-min consultation free.
Guide Chapters
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Frequently Asked Questions
What is state income tax nexus?
Connection creating state income tax obligation. Physical presence or economic nexus. CA Factor Presence: $711K sales or $71,154 property/payroll (2024). Other states have own thresholds.
What is PL 86-272?
Federal law (1959) protecting out-of-state sellers of tangible personal property from state income tax if activity limited to solicitation approved / shipped from outside state. Narrow protection.
Does PL 86-272 apply to services?
No. Only tangible personal property. Service providers not protected. Digital goods also outside protection.
How does CA apportionment work?
Single-sales factor post-2013. CA sales / total sales = CA portion. Market-based sourcing for services. Service revenue sourced to customer location.
What is combined reporting?
Unitary related entities file combined return. CA requires combined reporting. Water’s-edge election limits to U.S. operations.
What is water's-edge?
Election limiting combined report to U.S. operations. Election binding for years. Default is worldwide combined. Planning consideration.
What is market-based sourcing?
Service revenue sourced to state where customer receives benefit. CA uses market-based. Replaces cost-of-performance. Affects service businesses.
Does economic nexus apply to income tax?
Yes in many states post-Wayfair. CA Factor Presence test applies. Thresholds vary by state.
What is throwback?
Sales not taxable in destination state thrown back to origin. Creates higher apportionment in origin. CA uses throwback.
What about remote employees?
Often create employer nexus in employee’s state. COVID-era temporary relief mostly expired. Remote work nexus actively developing.
What is MTC?
Multistate Tax Commission. Uniform guidance on nexus, apportionment, compliance. MTC regulations influential but not binding on all states.
What's the new MTC PL 86-272 guidance?
MTC 2021 statement — internet activities beyond solicitation defeat PL 86-272 protection. Cookies, chat support, post-sale services. States adopting. Narrows protection significantly.
Should I file in every state with customers?
Only nexus states. Nexus analysis determines where. Evaluate before registering. Filing obligations recurring.
Next Steps
State income tax question? 15-min consultation free.
- CA Factor Presence: RTC §23101(b). PL 86-272: 15 USC §§381-384.
- Apportionment: CA RTC §25128. Combined reporting: RTC §25101.
Multistate exposure compounds quietly. Our California tax attorneys handle nexus analysis, voluntary disclosures, and audit defense.
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