State Income Tax Nexus 101

You hired your first remote employee in Texas. A sales rep was sent to work out of a co-working space in New York for a few months. You opened a small warehouse in Ohio to speed up shipping times. Your SaaS revenue crossed $100,000 in California. Each of these moves felt like a growth milestone. They were. They were also, in most cases, the moment your company became subject to tax obligations in a new state, whether you knew it or not. 

State income tax nexus is one of the most commonly misunderstood compliance challenges for growing startups and small businesses. Most founders focus on federal taxes and assume state taxes will sort themselves out later. They do not. The exposure compounds quietly while you are building, and the bill, when it arrives, includes back taxes, penalties, and interest that can stretch back years. 

Understanding how nexus works, and when your growth triggers it, is one of the most important tax conversations you can have before you think you need to have it. 

What Nexus Actually Means 

Nexus is the legal threshold that determines whether a state has the right to tax your business. If your company has nexus in a state, you are required to register, file returns, and pay applicable taxes there, even if you are incorporated elsewhere and never thought of that state as a place where you do business. 

The concept has two primary forms: physical nexus and economic nexus. Physical nexus is the older standard. It is triggered by a physical presence in a state, like an office, an employee, inventory in a warehouse, or even a salesperson who regularly works in the state. Economic nexus is newer and broader. It is triggered by a certain volume of sales into a state, regardless of any physical presence. 

Since the Supreme Court’s South Dakota v. Wayfair decision in 2018, every state with a sales tax has implemented economic nexus standards for sales and use tax. Income tax nexus rules have followed a similar trajectory. According to Zamp’s analysis of economic nexus adoption, universal adoption of economic nexus is now effectively complete, creating compliance obligations for virtually every multi-state seller. 

Remote Employees Are Your Fastest Nexus Creator 

For most startups today, the single fastest path to unintentional nexus is a remote workforce. When you hire an employee who lives and works in a state where your company has no other presence, that employee’s home state typically considers you to have nexus immediately. 

This creates a cascade of obligations: income tax registration, payroll tax withholding, potentially sales tax if you sell taxable goods or services into that state, and sometimes franchise or gross receipts taxes depending on the state’s structure. 

The challenge is that this happens automatically at the moment of hire, but the compliance burden often is not discovered until months or years later when a state catches up. By then, the liability includes not just the taxes owed, but substantial late-filing penalties and interest. 

The states most aggressively auditing for remote-worker nexus include California, New York, and Massachusetts, all states where remote employees are common, compliance thresholds are relatively low, and enforcement is robust. If you have hired remote workers in any of these states without registering and filing, you likely have exposure right now. 

Economic Nexus for Income Tax: The Threshold Question 

While economic nexus is most commonly discussed in the context of sales tax, many states have extended similar logic to income and franchise tax. According to Fusion CPA’s 2025 corporate tax analysis, understanding both rates and nexus rules is essential because state-level differences in apportionment and nexus can significantly affect your effective tax burden. 

Thresholds vary widely by state and by tax type. Some states trigger income tax nexus at $100,000 in receipts. Others use employee count, payroll thresholds, or property value. Some use a combination. A few states are more aggressive, asserting nexus based on the economic activity of a business’s customers, not just its own physical or economic footprint. 

For SaaS companies specifically, the picture is particularly complex. Digital products and services are treated differently across jurisdictions. A state that exempts SaaS from sales tax might still assert income tax nexus based on where your customers are located. The only reliable way to know your exposure is to analyze your revenue by state and cross-reference it against each state’s current nexus rules. 

What Most Growing Startups Miss 

There are several nexus triggers that catch founders off guard even when they have thought about the issue: 

1. Inventory in a third-party warehouse: If you use Amazon FBA or a similar fulfillment service, your inventory may be stored in states you never chose. Most fulfillment services store goods across multiple states based on their own logistics optimization, and each state where your inventory sits likely creates nexus. 

1. Attending trade shows or conferences: Some states take an expansive view of physical nexus and assert that sending a salesperson to a trade show even once creates nexus for that year. California, New York, and Texas are among the more aggressive states on this point. 

1. Intercompany transactions: If your parent company, subsidiary, or related entity has nexus in a state, many states have attribution rules that can pull your company into nexus as well. 

1. Crossing a revenue threshold mid-year: Economic nexus thresholds are typically measured on a rolling 12-month basis. If you cross a threshold in October, you may owe tax for transactions starting in November, even if you file on a calendar year basis. 

States are actively increasing their nexus audits, particularly for companies that have grown rapidly in recent years. As noted in the 2025 State Income Tax Guide, as states look for new revenue sources, audit activity around nexus compliance is increasing across the board. 

The Cost of Not Knowing 

Nexus non-compliance is not a minor oversight. It is a liability that grows every month it goes unaddressed. Penalties for failure to register in a state typically run between 5% and 25% of the tax owed, and interest accrues from the original due date. Some states can assess back taxes going back three to seven years, and a few have no statute of limitations for non-filers. 

The practical consequence is that a company that failed to register in two or three states for three years can easily face six-figure exposure that would not have existed if they had handled registration at the time nexus was created. 

Voluntary disclosure programs offer a path forward for companies that proactively identify and address past exposure. Most states participate in the Multistate Tax Commission’s voluntary disclosure program, which typically limits look-back periods to three or four years and may waive some penalties. But these programs require proactive action before the state initiates an audit. Once you are under audit, the opportunity closes. 

Getting in Front of the Problem 

The right time to conduct a nexus review is before you think you need one. If your business has hired remote employees, expanded sales into new states, used multi-state fulfillment, or seen meaningful revenue growth in the past two or three years, a formal nexus analysis is warranted. Escalon’s Tax Operations team works with startups and small businesses to evaluate nexus exposure across all 50 states, identify registration requirements, and develop a compliance strategy that addresses both current obligations and historical exposure. 

Growth is the goal. But unaddressed state tax exposure can turn your growth milestones into liability milestones. Understanding where you have nexus and handling it proactively is one of the clearest ways to protect the momentum you have worked hard to build. Talk to our tax team today to get a clear picture of where your business stands.