Traveling Employees: Multi-State Tax Withholding for Frequent Travelers

A traveling employee — a sales representative, a consultant, a regional manager, a corporate trainer — may perform work in a dozen or more states during a single year. Each day of work in a state potentially creates a state income tax withholding obligation for the employer and a state income tax liability for the employee. With 50 different state rules for day-count thresholds, de minimis exemptions, and reporting requirements, the compliance burden on employers with mobile workforces is substantial.

This article explains who qualifies as a traveling employee, the day-count problem, the state-by-state thresholds, the de minimis rule, the transportation employee exception, day-tracking strategies, withholding strategies, the employer registration burden, year-end reconciliation, the proposed Mobile Workforce legislation, a worked example, and the common mistakes employers make when managing traveling employee withholding.

Who is a "traveling employee"

A traveling employee is any worker who performs services in more than one state during the tax year. The category is broader than it sounds. Sales representatives who visit clients in multiple states are the obvious example, but the category also includes consultants who travel to project sites, regional managers who visit stores or offices, corporate trainers who deliver on-site sessions, auditors who rotate through client locations, and field service technicians. Any employee whose work takes them across state lines qualifies.

The category also includes employees who work remotely from a temporary location — an employee who works from a vacation home in another state for a few weeks, or who visits family in another state and works from there, may create traveling-employee withholding issues for the employer. The COVID-19 pandemic blurred the line between traveling employees and remote employees, as many workers became effectively mobile without changing job titles. Employers must look at where work is actually performed, not at job description or headquarters location.

The day-count problem

The day-count problem is the central compliance challenge for traveling employees. An employee who works 30 days in New York, 20 days in California, 15 days in Texas, and the remaining 235 days in their home state may have created withholding obligations in three states (NY, CA, and TX) in addition to the home state. Each state has its own rule for when withholding is required, and the rules do not coordinate. New York may require withholding from day one; California may require withholding from day one as well; Texas has no income tax but still requires SUI registration. The employer must understand and comply with each rule.

The day count must be precise. "Days worked in a state" generally includes any day on which the employee performs services in the state, even if the services are brief. Travel days to and from the state are typically counted as days worked, particularly if the employee performs any work on those days. Partial days in two states count as a day in each. The accumulation of partial days and travel days can push an employee over a threshold that the employee and employer did not realize had been crossed.

State day-count thresholds for withholding

State day-count thresholds for non-resident employee withholding vary widely. A few states require withholding from the first day the employee performs work in the state, regardless of how brief the work is. California is the most commonly cited example of a day-one state. New York also generally requires withholding from the first day, though certain exceptions apply. Other states have de minimis thresholds below which withholding is not required; these thresholds range from a low of 14 days to a high of 30 days, with 20 days also common.

The variations matter operationally. An employee who works 25 days in a 20-day-threshold state triggers withholding for the entire 25 days (or sometimes only for the days above the threshold, depending on the state). An employee who works 25 days in a 30-day-threshold state does not trigger withholding at all. The employer must track the day count in each state and apply the threshold rule for each state separately. Multi-state payroll software can automate this, but the underlying data — accurate day counts by state — must be captured contemporaneously.

Examples of state thresholds

Illinois has a 30-day safe harbor for non-resident employees, meaning no withholding is required if the employee works 30 days or fewer in Illinois during the calendar year. Indiana also has a 30-day safe harbor. Montana and West Virginia have 30-day safe harbors as well. Alabama enacted a 30-day safe harbor effective January 1, 2026, under Act 2025-334. Colorado, by contrast, generally requires withholding from day one. New York requires withholding from day one, though there are narrow exceptions. California requires withholding from day one for non-resident employees performing services in California.

The lack of a uniform national rule is the reason the proposed Mobile Workforce State Income Tax Simplification Act (discussed below) has been introduced in Congress repeatedly. Until a national safe harbor is enacted, employers must comply with the patchwork of state rules.

The "de minimis" rule in some states

The de minimis rule is the threshold below which a state does not require withholding for non-resident employees. The rule is a concession to administrative practicality — states recognize that requiring withholding for a single day of work is more burdensome than the tax it would generate. The de minimis threshold varies by state, with 30 days being a common threshold but with significant variation. Some states have no de minimis threshold at all and require withholding from day one.

The de minimis rule is not uniform in its mechanics. Some states exempt the first 30 days entirely (no withholding for any of the 30 days if the threshold is not exceeded). Other states require withholding retroactively for all days if the threshold is exceeded (so an employee who works 31 days in a 30-day-threshold state has withholding for all 31 days, not just the 31st day). The distinction matters for both employer cash flow and employee tax planning. Employers should consult the specific state's rule to determine the mechanics.

The transportation employee exception

Transportation employees — airline pilots, flight attendants, truck drivers, train crews, and certain maritime workers — are subject to special federal rules that override state day-count requirements. The federal rules, codified at 49 U.S.C. §40116 for air carriers and at related provisions for other transportation modes, generally source transportation employee compensation to the employee's residence state or to the employer's principal place of business, rather than to every state the employee passes through.

The rationale is straightforward. An airline pilot may pass through 20 states in a single shift. Requiring withholding in each state would be administratively impossible and would generate tiny amounts of tax per state. The federal rules simplify the analysis by sourcing the compensation to one or two states, typically the employee's residence and the employer's location. The rules are complex, and transportation employers should consult specialized payroll counsel to ensure compliance, but the basic principle is that transportation employees are exempt from the day-count analysis that applies to other traveling employees.

49 U.S.C. §40116 in detail

Section 40116 of Title 49 of the U.S. Code provides that compensation of an air carrier employee is subject to income tax only in the employee's state of residence, the employee's domicile, or the state in which the employer's principal place of business is located. The provision preempts state day-count rules for air carrier employees, who are subject to taxation only in those three potential states. Similar rules apply to railroad employees under the Railroad Unemployment Insurance Act and to motor carrier employees under certain conditions. The provisions are narrow and apply only to specific transportation categories, but within those categories they significantly simplify compliance.

How to track days worked per state

Effective day tracking combines several tools. The foundation is a calendar log maintained by the employee, recording the work location for each workday. The log should be contemporaneous — reconstructed calendars are less credible to auditors — and should distinguish between workdays, travel days, and personal days. Calendar logs can be maintained in a shared spreadsheet, in dedicated mobile-workforce apps, or in the employer's HR information system.

Travel itineraries from corporate travel systems provide corroborating evidence. If the employer uses a corporate travel agency or booking platform, the itineraries show where the employee traveled and on what dates. Time-tracking software that captures work location provides another layer of evidence. Mobile-workforce-specific apps (such as those offered by several providers in the HR technology space) use geolocation to record the employee's location at check-in, providing automated day tracking. The combination of these sources, with cross-references to expense reports and credit card receipts, builds a defensible audit trail.

Withholding strategies for traveling employees

Employers have several strategies for managing traveling-employee withholding, each with trade-offs. The choice of strategy depends on the number of traveling employees, the number of states involved, the sophistication of the payroll system, and the employer's risk tolerance. There is no single right answer; the best strategy depends on the specific situation.

Default to residence-state withholding

The most common strategy is to default to residence-state withholding for the traveling employee. The employer withholds state income tax for the employee's state of residence on all wages, regardless of where the work is performed. This approach is simple and ensures that the employee's home state tax is paid. The risk is that non-resident states where the employee works may also require withholding, particularly if day-count thresholds are crossed. The employee may owe additional tax in those states at year-end, with potential underpayment penalties.

Multi-state withholding

A more sophisticated strategy is to perform multi-state withholding, allocating wages to each state where the employee works based on the day count. This requires the payroll system to support per-day or per-state allocation, which most modern payroll platforms do. The employer withholds for each state where the employee works, in proportion to the days worked. This approach minimizes year-end surprises for the employee but requires accurate day tracking and registration in each state where withholding is required.

The "primary work state" approach

A practical compromise is the primary work state approach: the employer withholds only in the state where the employee works the most days, treating that state as the employee's work state for the year. This approach simplifies payroll and reduces the registration burden. The risk is non-compliance in other states where the employee works. The primary-work-state approach is not a legal safe harbor in most states, and an audit could uncover withholding failures. Employers that use this approach should document their analysis and be prepared to defend it.

Employer registration burden

Each state where a traveling employee triggers withholding requires the employer to register for income tax withholding with the state revenue agency. Registration typically takes two to six weeks and may require a deposit or bond. The employer must also register for SUI if it has employees performing services in the state (subject to the localization rules discussed in our article on state unemployment insurance). New-hire reporting under 42 U.S.C. §653a is required in each state where an employee works. Workers' compensation coverage must extend to each state where the employee works.

The registration burden can be substantial for employers with many traveling employees. A company with 50 traveling employees, each working in 5 states, may face 50 to 100 state registrations (with overlap, since multiple employees may work in the same state). The cost of registration, ongoing compliance, and the staff time to manage the registrations can be significant. This is one of the reasons employers consider PEO or EOR arrangements (discussed in our article on PEO and EOR solutions) — a PEO is already registered in all 50 states and can absorb much of the registration burden.

Year-end reconciliation

Year-end reconciliation for traveling employees is complex. The W-2 must reflect the wages and withholding for each state where the employee worked. An employee who worked in six states during the year should receive a W-2 with six state wage boxes, each showing the wages allocated to that state and the tax withheld. The employee must file state income tax returns in each state where they had income, including non-resident returns in states where they are not resident. The employee may also be entitled to a multi-state credit on their resident state return, as discussed in our article on multi-state tax credits.

Employers should reconcile the multi-state withholding at year-end, comparing the day counts to the withholding actually performed. Discrepancies — for example, where the employee worked more days in a state than were captured in the withholding system — should be corrected before W-2 issuance. Supplemental withholding in the final pay period can true up the withholding if a shortfall is identified. Employers should also confirm that the W-2 state wage boxes match the day-count allocation, because mismatches are a common audit trigger.

The proposed Mobile Workforce bill

The Mobile Workforce State Income Tax Simplification Act (S. 1443), reintroduced in April 2025 by Senators John Thune and Sherrod Brown, would create a national 30-day safe harbor for non-resident employee withholding. Under the bill, no state could require withholding or impose non-resident income tax on an employee who is present in the state for 30 days or fewer during the calendar year. The bill has been introduced in multiple Congresses and has consistently passed the Senate Finance Committee but has not received a floor vote.

The bill has broad support from the American Institute of Certified Public Accountants (AICPA), the American Payroll Association (APA), the Council on State Taxation (COST), and the Society for Human Resource Management (SHRM). Supporters argue that the bill would dramatically simplify compliance for employers and employees, eliminating the patchwork of state day-count rules. Opponents, primarily state revenue departments, argue that the bill would reduce state revenue and that the 30-day threshold is too generous. Our article on the Mobile Workforce bill covers the legislation in detail.

Worked example: a consultant in six states

Consider a consultant who lives in Virginia and works for a consulting firm headquartered in Washington, D.C. During the tax year, the consultant performs work in six states: 150 days in Virginia (the home state), 60 days in New York (client project), 40 days in California (client project), 30 days in Illinois (client project), 20 days in Massachusetts (client project), and 65 days of travel, training, and personal time outside any work state. The total workdays are 300, with the remaining 65 days allocated to non-work.

Under default residence-state withholding, the employer withholds Virginia tax on all wages. The consultant owes Virginia resident tax on all income, with potential credits for taxes paid to other states. The consultant also owes non-resident tax in New York (60 days exceeds the day-one threshold), California (40 days exceeds the day-one threshold), Illinois (30 days, at the safe harbor threshold — no withholding required but the consultant may still owe tax if the threshold is exceeded), Massachusetts (20 days, depending on the Massachusetts threshold), and Virginia (resident). The consultant will face multiple non-resident filings and a complex credit computation on the Virginia return.

Under multi-state withholding, the employer withholds in each state based on the day count. The consultant's W-2 shows six state wage boxes, with withholding in each. The consultant still must file in each state, but the underpayment risk is reduced. The employer must register for withholding in New York, California, Illinois, and Massachusetts (Virginia is already registered as the residence state). The administrative burden is significant, but the consultant's year-end tax situation is more predictable. For a consulting firm with many traveling consultants, multi-state withholding is typically the right approach.

Common mistakes

Several mistakes are common. Under-withholding is the most frequent — the employer defaults to residence-state withholding, the employee works enough days in non-resident states to trigger withholding, and the employee is surprised at year-end with a multi-state tax bill and possible underpayment penalties. Missing state registrations is another common error — the employer withholds in a state but is not registered, exposing the employer to penalties and back taxes. Employee surprise at tax time is the predictable consequence of poor communication: the employer should inform traveling employees of the multi-state implications of their travel and should provide year-end summaries of the state-by-state day counts and withholding.

Other common mistakes include failing to track partial days correctly (counting a two-hour visit as a full day in one state and missing that it also counts as a partial day in another), failing to apply the transportation employee exception when it applies (resulting in unnecessary withholding in many states), and failing to reconcile the W-2 state wage boxes with the day-count allocation (a common audit trigger). Each of these mistakes can be avoided with good processes and modern payroll software.

What to do next

If you have traveling employees, take three steps. First, implement a day-tracking system — a calendar log supported by travel itineraries and time-tracking software — that captures the state-by-state work location for each traveling employee. Second, identify the states where each employee has crossed withholding thresholds and confirm that the employer is registered for withholding in each such state. Third, communicate with traveling employees about the multi-state tax implications of their travel, and provide year-end summaries of state-by-state day counts. Run our multi-state withholding calculator to estimate the tax impact, and consult a licensed tax professional for your specific situation.