Multi-state tax has become the single largest compliance workload for growing U.S. businesses. A remote hire, a trade show, a warehouse, or crossing an economic nexus threshold can each create filings in a new state. This guide walks through the four nexus tests, apportionment, PTET, and the compliance calendar that keeps everything on track.
The Four Nexus Tests Every Business Should Know
Physical nexus: employees, contractors working under direction, offices, warehouses, or inventory physically located in a state. Any of these creates both income tax and sales tax nexus in most states.
Economic nexus: since the 2018 Wayfair decision, nearly every state enforces a sales-tax economic nexus threshold (commonly $100,000 in sales or 200 transactions in the prior or current year). Several states also assert economic nexus for income tax at similar thresholds.
Factor presence nexus: states like California assert income tax nexus when property, payroll, or sales exceed defined thresholds ($711,538 sales in California for 2024). Affiliate and click-through nexus: historical rules based on affiliates or referral programs within the state still apply in some jurisdictions.
Apportionment: How Income Gets Divided Among States
Once a business has income tax nexus in multiple states, total income is divided among those states using apportionment. Most states now use single sales factor apportionment (100% weight on where the sales are delivered or sourced). A minority still use three-factor (sales, payroll, property).
Sourcing rules vary. Tangible goods are sourced to the destination. Services are sourced to where the benefit is received (market-based sourcing) in most states, or to where the service is performed (cost-of-performance) in a shrinking minority. Digital products split the difference depending on state.
Getting apportionment wrong in either direction costs money. Over-apportioning to a high-tax state creates an overpayment; under-apportioning triggers assessments with penalties.
PTET: The SALT Cap Workaround Most Eligible Businesses Should Use
The 2017 Tax Cuts and Jobs Act capped the state and local tax (SALT) deduction at $10,000 for individuals. Thirty-plus states responded with Pass-Through Entity Tax (PTET) elections: the entity pays state tax at the entity level (deductible against federal income) and passes a credit to the owners.
PTET elections save roughly the top federal rate (37%) times the state tax amount. For a $100,000 state tax bill, that is a $37,000 federal savings. The election is time-sensitive (quarterly or annual depending on state) and not automatic. Missing the election window is a real and recurring mistake.
Sales Tax: More States, More Filings, More Software
A business with sales tax nexus in 10 states files 10 returns at different frequencies (monthly, quarterly, annual) with different forms. Manually filing 10 state returns consumes 30 to 50 hours a month. Sales tax automation (Avalara, TaxJar, Anrok, Stripe Tax, Vertex) is almost always the right answer at that volume.
Automation requires correct configuration: nexus registrations, product taxability, exemption certificates, and filing calendars. We set up and operate the sales tax stack for clients across dozens of states.
Payroll Tax: The Forgotten Multi-State Obligation
Each state with a remote employee requires state unemployment (SUTA) registration, state income tax withholding registration, and sometimes state disability or paid family leave. A single remote hire in a new state triggers three or four registrations.
Payroll providers (Gusto, Rippling, ADP) handle registration and filing for most states. The business still has to approve registrations, respond to state agency notices, and track ongoing rate changes.
The Voluntary Disclosure Path for Historical Exposure
Businesses that discover unfiled state returns have two main paths: register forward and accept prior exposure, or negotiate a Voluntary Disclosure Agreement (VDA) with a limited look-back (usually 3 to 4 years) and penalty waiver in exchange for voluntary compliance.
VDAs are the right answer when exposure is large, the state is aggressive (California, New York, Texas, and a handful of others), and the business can complete the agreement before any state contact. We manage the negotiation anonymously and close it before registration.
Compliance Calendar: The Only Thing That Actually Works
Multi-state businesses need one calendar that captures every state filing. Ours includes state income tax (annual and quarterly estimates), franchise or margin tax, sales tax (monthly, quarterly, annual), PTET elections and payments, payroll SUTA and withholding, annual reports, and business license renewals.
Without a calendar, a business with 10-state nexus misses roughly two to four filings per year. Each miss is a penalty.
Case Study Pattern: The $8M SaaS Company With Twelve-State Exposure
Remote Work, Traveling Executives, and Convenience-of-Employer Rules
Some states (most notably New York, Delaware, Nebraska, Pennsylvania) apply a convenience-of-employer rule that taxes wages earned by remote workers in the employer's state if the remote work is for employee convenience rather than employer necessity. A New York employer with a Florida-based remote hire can still owe New York withholding on the full wages.
Traveling executives create similar complexity. Days worked in California, New York, and Massachusetts can each trigger state income tax sourcing, even for brief visits. We build state-by-state policies for clients whose leadership teams travel heavily.
Economic Nexus Beyond Sales Tax
Sales tax gets the attention, but several states now apply economic nexus to corporate income tax as well. Ohio, Washington, and California each assert income tax nexus at defined thresholds based on sales, property, or payroll in the state. The implications are larger than sales tax: apportionment, combined reporting, and franchise tax exposure all follow.
A growing ecommerce or SaaS business can easily acquire income tax nexus in a dozen states during a single year of growth. We map both sales tax and income tax nexus in every nexus review.
If I only have one remote hire, do I really need all these filings?
In that hire's state, yes: SUTA, withholding, often state income tax nexus, and potentially sales tax nexus. We scope the full obligation before the hire starts.
How far back will states look?
Without a VDA, states can often go back indefinitely for unfiled returns and 3 to 10 years for under-reported returns. With a VDA, the look-back is typically capped at 3 to 4 years.
Is a PTET election always beneficial?
For profitable pass-through owners with state tax above the SALT cap, yes in most states. Model the cash flow impact; some states are neutral at lower profit levels.
Which states are the most aggressive?
California, New York, Texas, Massachusetts, and Washington all have active enforcement programs. Florida, Nevada, and South Dakota have no state income tax but still enforce sales tax.