What Triggers the WARN Act: Closings, Mass Layoffs, and Exceptions

Two events trigger the WARN Act at a covered employer: a plant closing that costs 50 or more full-time workers their jobs within a 30-day period, or a mass layoff that meets specific headcount and percentage thresholds at a single site within the same window.¹ Cross either line and the employer owes 60 days’ advance written notice to workers, the state, and local government. Miss the notice and the employer owes up to 60 days of back pay and benefits to every affected worker.

Which Employers Are Even Covered

The triggers only matter if the employer is big enough for the statute to reach in the first place. A business is covered if it has 100 or more full-time employees. It’s also covered if its total workforce, including part-timers, logs at least 4,000 hours per week, excluding overtime.¹

“Part-time” has a specific meaning here: anyone averaging fewer than 20 hours per week, or anyone employed for fewer than 6 of the previous 12 months. Those workers don’t count toward the 100-employee coverage threshold, and they don’t count when calculating whether a specific closing or layoff crosses the trigger numbers below. They are still entitled to receive notice if a triggering event occurs.

Plant Closing Trigger

A plant closing is a permanent or temporary shutdown of a single employment site, or of a facility or operating unit within that site, that eliminates jobs for 50 or more full-time employees within any 30-day period.¹ The whole business doesn’t have to close. Shutting down one department, one production line, or one operating unit at a facility can trigger the law as long as 50 full-time workers lose their jobs.

The phrase “single site of employment” carries more weight than it looks. A campus, an industrial park, or a group of nearby buildings can count as one site. Separate warehouses in the same area where the employer rotates the same workers between buildings qualify as a single site.² Two facilities on opposite sides of a city with different workers and separate management are treated as separate sites, even under one owner. Remote workers and traveling employees are assigned to whichever home base appears in the employer’s organizational structure.

Mass Layoff Trigger

A mass layoff is a workforce reduction at a single site that does not involve shutting the facility or an operating unit. There are two ways to hit the trigger:¹

At least 50 full-time employees lose their jobs within a 30-day period, and those workers represent at least 33 percent of the site’s full-time workforce.
At least 500 full-time employees lose their jobs within a 30-day period. At that level, the percentage test drops away.

The dual threshold on the first track is where employers miscalculate. A company with 300 full-time employees at a site can lay off 60 people without triggering the law, because 60 is only 20 percent of the workforce. The same 60 layoffs at a site with 150 full-time employees cross the 33 percent line and trigger the notice requirement. Raw headcount alone is not the answer; the percentage matters just as much when a site is smaller.

What Counts as a Job Loss

The trigger numbers only count “employment losses,” which the statute defines in three ways:¹

Involuntary termination for any reason other than misconduct, voluntary resignation, or retirement.
A layoff that stretches beyond six months, even if the employer originally called it temporary.
An hours reduction of more than 50 percent every month for a six-month period.

Voluntary quits, retirements, and discharges for cause are excluded from the count. That distinction is where some employers try to move the goalposts. A permanent cut relabeled as a temporary layoff still counts as an employment loss once six months pass, and the notice obligation applies retroactively.

Transfers Within the Same Company

When a business relocates or consolidates operations, a job elimination doesn’t count as an employment loss if the employer offers a transfer before the closing or layoff. If the new workplace is within a reasonable commuting distance, the offer alone removes that employee from the count, whether or not the worker accepts.³ If the new site is farther away, the transfer only avoids an employment loss if the employee actually accepts within 30 days of the offer or 30 days of the closing, whichever comes later.⁴ The break in employment can’t exceed six months, and the new position can’t amount to a constructive discharge through gutted pay or drastically changed responsibilities.

Sales of the Business

When a company changes hands, the seller carries the notice obligation up to and including the closing date of the sale. After the sale, the buyer takes it over.³ Workers employed by the seller on the closing date are treated as employees of the buyer immediately afterward, so the headcount carries over. A buyer planning layoffs shortly after an acquisition needs early coordination with the seller, because the 60-day clock doesn’t pause for a transaction.

The 90-Day Aggregation Rule

Employers can’t dodge the law by spacing out smaller rounds of cuts. The statute uses a rolling 90-day window: if separate groups of job losses at the same site each fall below the trigger numbers individually but together exceed them, the law treats the total as a single plant closing or mass layoff.⁵

The only way out is proving that each round of cuts had genuinely separate and unrelated causes. An employer who lays off 30 people in January because a contract ended, then another 25 in March because of an unrelated budget shortfall, has a plausible argument. An employer who splits a single restructuring into three waves to keep each one under 50 heads does not. The burden of proof falls squarely on the employer.

Exceptions That Shorten or Excuse Notice

Three statutory exceptions let an employer give fewer than 60 days’ notice once a triggering event is on the horizon. In all three, the employer must still provide as much notice as circumstances allow and give a written explanation of why the full 60 days wasn’t feasible.⁵

Faltering company. This exception applies only to plant closings, not mass layoffs. The employer must have been actively pursuing financing or new business that would have kept the facility open, and must have reasonably believed in good faith that announcing the shutdown would have scared off the deal.
Unforeseeable business circumstances. The closing or layoff resulted from conditions the employer couldn’t reasonably have predicted when the 60-day window opened. Examples include a major client abruptly canceling a contract or a strike at a key supplier.⁶
Natural disaster. No notice is required at all when a plant closing or mass layoff is the direct result of a flood, earthquake, drought, or similar event.

Employers lean on these exceptions more than the facts support. Courts look at what the employer actually knew and when, not what it claims in hindsight. A company that watched revenue decline for months can’t call the final contract loss unforeseeable just because it felt sudden.

One Boundary Worth Knowing

Federal WARN is not the whole picture. More than a dozen states have their own mini-WARN laws, and many set stricter rules: lower employer-size thresholds (75 or even 50 employees), lower layoff triggers (as few as 15 or 25 workers), and in at least one state a 90-day notice period. These laws operate alongside the federal statute. An event that doesn’t trigger federal WARN can still trigger a state notice obligation, so the state-law check belongs on the same page as the federal analysis.

1
Office of the Law Revision Counsel. 29 USC Ch. 23 – Worker Adjustment and Retraining Notification
2
U.S. Department of Labor. Single Site of Employment
3
Office of the Law Revision Counsel. 29 U.S. Code 2101 – Definitions; Exclusions From Definition of Loss of Employment
4
U.S. Department of Labor. WARN Advisor
5
Office of the Law Revision Counsel. 29 USC 2102 – Notice Required Before Plant Closings and Mass Layoffs
6
eCFR. 20 CFR 639.9 – When May Notice Be Given Less Than 60 Days in Advance?