Employer Nexus Explained: When Must You Register in an Employee's State?

Nexus is the threshold question in state payroll tax compliance. Without nexus, a state cannot require an employer to register, withhold, or report. With nexus, the full range of state payroll obligations attaches, including income tax withholding, state unemployment insurance registration, wage-and-hour compliance, and in some cases corporate franchise tax. The rise of remote work has dramatically expanded the universe of employers with nexus in multiple states, often inadvertently. Understanding when nexus arises, what it triggers, and how to manage it is essential for any employer with cross-state operations.

What "nexus" means in the payroll tax context

Nexus, in the state tax context, refers to a connection between an employer and a state that is sufficient to justify the state's exercise of taxing and regulatory authority over the employer. In the payroll tax context, nexus is the threshold that triggers the employer's obligations to register for state tax accounts, withhold state income tax from employee wages, pay state unemployment insurance, and comply with state wage-and-hour laws. Without nexus, none of these obligations apply.

The concept of nexus derives from the U.S. Constitution's Due Process and Commerce Clauses, which require a minimum connection between the taxpayer and the state before the state can impose tax. For most of the twentieth century, that connection required physical presence. The Supreme Court's 2018 decision in South Dakota v. Wayfair expanded the concept of nexus for sales tax purposes by allowing states to assert economic nexus based on the volume of sales into the state, without any physical presence. The expansion has been most consequential for sales tax, but the trend has begun to affect income tax and, to a lesser extent, payroll tax.

Physical nexus

Physical nexus remains the historical standard and the most common basis for payroll tax nexus. Physical nexus arises when an employer has a tangible presence in the state, such as an office, a warehouse, a retail location, or an employee physically present. The presence need not be substantial: a single employee regularly working in the state is generally sufficient to establish physical nexus for payroll tax purposes. The standard reflects the principle that an employer with employees physically present in a state is meaningfully connected to that state.

Physical nexus is straightforward in concept but can be subtle in application. A traveling employee who spends a few days per year in a state may or may not create nexus, depending on the state's day-count thresholds and the nature of the work. A remote employee who lives and works in the state full-time almost always creates nexus. An independent contractor generally does not create nexus for the engaging business, although the analysis can be more complex if the contractor functions as a de facto employee.

Economic nexus

Economic nexus, as expanded by Wayfair, arises when an employer's level of economic activity in a state exceeds a threshold, even without any physical presence. For sales tax, most states now assert economic nexus based on annual sales into the state exceeding $100,000 or 200 transactions. For income tax, a growing number of states assert economic nexus based on similar thresholds, although the constitutional basis is less settled than for sales tax. For payroll tax, economic nexus remains less common, and most states continue to require some form of physical presence or employee activity in the state.

The emerging trend is toward broader assertion of economic nexus across tax types. Some states have begun to assert economic nexus for franchise or corporate income tax based on sales or revenue thresholds. For payroll tax specifically, the employee-presence rule remains the dominant trigger, but employers should monitor developments. Employers with substantial economic activity in a state but no employees there should consult with state tax counsel about potential income tax exposure.

Employee presence as a nexus trigger

For payroll tax purposes, employee presence is the dominant nexus trigger. A single W-2 employee physically present in a state generally creates nexus for that state's payroll taxes, including income tax withholding and state unemployment insurance. The rule is robust: the employee need not be a manager, need not work full-time, and need not be the employer's only employee in the state. Regular presence in the state for employment purposes is sufficient.

Some states apply day-count thresholds for traveling employees. A state may provide that an employee's presence does not create nexus until the employee works in the state for more than a specified number of days in a year. The thresholds vary by state and by tax type, with common thresholds including 14, 21, or 30 days. These thresholds are most often applied to income tax withholding rather than to SUI, and the rules differ from the income tax reciprocity rules that apply between certain pairs of states. Employers with traveling employees should consult each state's specific rules to determine when nexus arises.

The thresholds

Most states apply a one-employee rule for nexus: a single W-2 employee physically present in the state creates nexus for that state's payroll taxes. This rule applies in California, Texas, New York, Florida, and most other states. The rule is unforgiving: an employer who hires a remote employee in California without first registering for California payroll tax accounts is technically in noncompliance from the employee's first day of work.

Some states apply day-count thresholds for traveling employees. New York applies a 14-day threshold for certain withholding obligations for traveling employees, although the rule interacts with the convenience rule in complex ways. California applies strict physical presence rules with limited day-count exceptions. The specific thresholds vary by state and by tax type, and the rules can interact in complex ways for employees who travel regularly.

What nexus triggers

Nexus in a state typically triggers a suite of state payroll obligations. The first is state income tax withholding: the employer must register for a withholding account, withhold state income tax from employee wages according to the state's withholding tables, and remit the withheld tax on the state's deposit schedule. The second is state unemployment insurance: the employer must register for an SUI account, pay quarterly SUI tax on wages up to the state's wage base, and file quarterly wage reports.

The third is state wage-and-hour compliance. The employer must comply with the state's minimum wage, overtime, meal and rest break, pay stub, and final paycheck rules, which often differ from federal rules and from the rules of other states. California, for example, requires daily overtime for hours worked beyond 8 in a day, while most other states follow the federal 40-hour weekly standard. The fourth is workers compensation coverage: the employer must maintain workers compensation insurance that covers employees in the state, often through a state-specific policy or endorsement.

The fifth, in some cases, is franchise or corporate income tax. An employer with nexus in a state may also have income tax exposure, particularly if the employer's income is apportioned to the state based on the payroll, property, and sales factors. The income tax analysis is separate from the payroll tax analysis and can produce surprising results for employers with employees in states where they have no other operations.

The PEO and EOR alternative

A Professional Employer Organization or Employer of Record can absorb the registration burden by becoming the legal employer for payroll purposes in the employee's state. Under a PEO or EOR arrangement, the PEO or EOR registers for state tax accounts, withholds and remits state income tax, pays SUI, files wage reports, and handles state wage-and-hour compliance under its own state account numbers. The client employer pays a service fee, typically a percentage of payroll or a per-employee per-month charge, and remains the worksite employer for day-to-day supervision.

The PEO and EOR alternatives can be cost-effective for employers with one or two employees in a state where they do not otherwise operate. The arrangement avoids the administrative burden of registering for state tax accounts, learning the state's wage-and-hour rules, and maintaining state-specific workers compensation coverage. However, the cost can be significant, and the structure must be respected as a genuine co-employment arrangement rather than a sham designed solely to avoid state registration. The PEO or EOR must actually perform the employer functions, and the client employer must not retain the indicia of employment that would undermine the co-employment characterization.

Remote work and the new nexus problem

The rise of remote work has dramatically expanded the universe of employers with nexus in multiple states. An employer that previously had all employees in a single state may now have employees scattered across the country, each creating nexus in their home state. Hiring a remote employee in a new state triggers the full range of state payroll obligations from the employee's first day of work, and failure to register before the first payroll can produce back-registration requirements, back taxes, penalties, and interest.

The remote work nexus problem has several dimensions. The first is the registration burden: an employer with employees in 20 states must maintain 20 separate compliance calendars. The second is the wage-and-hour burden: each state has its own minimum wage, overtime, pay stub, and final paycheck rules. The third is the SUI burden: each state has its own SUI wage base and rate structure. The fourth is the workers compensation burden: each state has its own coverage requirements.

Nexus versus apportionment

Nexus and apportionment are related but distinct concepts. Nexus is binary: an employer either has nexus in a state or it does not. If nexus exists, the state can require registration, withholding, and reporting. Apportionment determines how much of the employer's income is taxable in the state, typically based on a formula considering payroll, property, and sales in the state relative to the employer's totals. An employer can have nexus in a state but apportion very little income there, particularly if the employer has minimal property and sales in the state.

The distinction matters because the nexus analysis triggers registration and withholding obligations, while the apportionment analysis determines the income tax cost. An employer with employees in a state but no property or sales in the state may have nexus for payroll tax purposes but minimal income tax exposure. Conversely, an employer with substantial sales in a state but no employees may have economic nexus for income tax purposes under post-Wayfair rules. The two analyses should be conducted separately and coordinated with overall state tax planning.

State-by-state differences

States differ significantly in their nexus enforcement posture. California is among the strictest, asserting nexus for any employee presence in the state and applying aggressive wage-and-hour enforcement. Texas, despite having no state income tax, requires SUI registration and reporting for any employee in the state and applies strict workers compensation rules for certain industries. New York is similarly strict, asserting nexus for any employee presence and applying its convenience rule to non-resident teleworkers. Florida has no state income tax but still requires SUI registration and reporting for in-state employees.

Other states vary in their enforcement posture. Some states have day-count thresholds for traveling employees, while others assert nexus from the first day of presence. Some states have reciprocal agreements with neighboring states that modify the withholding analysis for cross-border employees. Employers should consult each state's specific rules and should not assume that the rules of one state apply in another.

The cost of getting nexus wrong

The cost of getting nexus wrong can be substantial. Back taxes are the most direct cost: an employer that failed to withhold state income tax or pay SUI must remit the unwithheld amounts, plus interest. Penalties can add significantly to the cost, particularly for willful failures or for failures that continue over multiple quarters or years. Back-registration requirements can produce additional administrative cost, and some states impose registration penalties for late registration.

Beyond the direct tax cost, getting nexus wrong can produce wage-and-hour exposure. An employer that did not comply with the state's minimum wage, overtime, pay stub, or final paycheck rules may owe back wages, liquidated damages, and attorney's fees. Workers compensation exposure can be similarly significant: an employer without proper coverage in the state may be liable for the full cost of any workplace injury, plus penalties. Multi-state employers should treat nexus assessment as a foundational compliance task and should not delay registration beyond the employee's first day of work.

How to assess your company's nexus footprint

Assessing a company's nexus footprint requires a systematic review of where the company has employees, property, and sales. The first step is to compile a list of all employees and their work locations, including remote and traveling employees. The second step is to compile a list of all company property, including offices, warehouses, equipment, and inventory. The third step is to compile a list of all sales by state, including sales to in-state customers and sales delivered to in-state addresses.

The fourth step is to map each entry to the corresponding state nexus rules. For employee presence, identify each employee's regular work location and confirm whether the state applies a one-employee rule or a day-count threshold. For property and sales, confirm whether the activity creates physical or economic nexus. The result is a nexus map that identifies the states where the company has registration, withholding, and reporting obligations.

Common employer mistakes

Several common mistakes generate nexus exposure and unnecessary cost. The first is hiring a remote employee before registering in the employee's state, which produces back-registration requirements and back taxes. The second is missing SUI registration, particularly in states with no income tax, where employers may assume no state registration is required at all. The third is forgetting state-specific wage laws, particularly in states like California with rules that differ significantly from federal rules. The fourth is failing to maintain workers compensation coverage in each state where the company has employees.

Another common mistake is treating nexus as a one-time analysis rather than an ongoing obligation. States periodically update their nexus rules, particularly in the post-Wayfair environment, and an employer's nexus footprint can change as the company hires, opens new locations, or expands sales. Employers should periodically reassess their nexus footprint, ideally annually, and should update their compliance posture as the footprint changes. A simple checklist can help ensure that each new hire triggers the appropriate state registration and compliance steps before the first payroll.

What to do next

If your company has employees in multiple states, start by compiling a complete list of employee work locations and identifying the states where the company has nexus. Confirm that the company is registered for state income tax withholding and SUI in each state where it has employees, and verify that workers compensation coverage extends to each state. If you are hiring a remote employee in a new state, complete the registration before the employee's first day of work. Run our multi-state withholding calculator to verify withholding calculations for employees in each state, and consult a licensed tax professional for a comprehensive nexus review if your footprint is complex or has not been recently assessed.