An employer announces 20 layoffs in January, 25 more in February, and 30 in March — all at the same plant. No single round looks big enough to trigger the federal WARN Act. Added together, though, the total is 75 workers in under 90 days, and that can change everything.
That is the point of the WARN Act's 90-day aggregation rule: an employer cannot avoid giving 60 days' notice simply by splitting one layoff into smaller pieces.
The thresholds it protects
The federal WARN Act generally requires 60 days' written notice before two kinds of events at a covered employer — one with 100 or more full-time employees:
- A plant closing: the permanent or temporary shutdown of a single site of employment that causes employment loss for 50 or more full-time employees during any 30-day period.
- A mass layoff: an employment loss during any 30-day period for either 500 or more full-time employees, or 50 to 499 full-time employees who make up at least 33 percent of the full-time workforce at that site.
Those 30-day windows are where splitting could work: a company laying off 40 workers every few weeks would never cross a threshold in any single 30-day period. The aggregation rule closes that gap.
How the rule works
Under the WARN regulation, employment losses that occur within any 90-day period are added together to decide whether a plant closing or mass layoff has occurred. If the combined total reaches the threshold — 50 or more for a closing, or the mass-layoff test — the event is covered, even though no single round crossed the line on its own.
A simple example shows the logic. Suppose a warehouse employs 200 full-time workers and lays off 30 in week one, 25 in week five, and 20 in week eleven. Each round alone is below 50. Together they total 75 workers — more than 33 percent of the site's workforce — within 90 days. That combined loss can qualify as a mass layoff, and the workers would have been owed 60 days' notice. Losses separated by more than 90 days, by contrast, are not combined, so two rounds of 40 layoffs six months apart do not aggregate into an 80-worker event.
The exception: separate and distinct causes
Aggregation is not automatic. The regulation gives the employer a way out: if it can show that the losses resulted from separate and distinct actions and causes, and were not an attempt to evade the WARN Act, the rounds are not combined.
Losing two unrelated contracts at different times, for different business reasons, is the kind of case an employer would point to. What the employer cannot do is point to a single decision — one restructuring, one closure plan, one lost customer — and claim each round was independent just because the departures were staggered. The burden is on the employer to make that showing: workers do not have to prove the rounds were connected; the employer has to prove they were not.
What this means for workers reading a notice
If you were laid off and your employer says no WARN notice was required because your group was too small, ask what else happened at your site in the previous 90 days. Other rounds at the same location — even in different departments — may count toward the same total if they stem from the same cause.
A few practical points:
- Count the site, not the company. Aggregation applies at a single site of employment. Layoffs at a plant in Ohio do not combine with layoffs at an office in Texas, even if the same company owns both.
- Count full-time workers. The federal thresholds count full-time employees. Part-time workers are generally not counted toward the thresholds, though they are still entitled to notice if a covered event occurs.
- Watch the calendar, not the announcement. The 90-day window runs from the dates of employment loss, not the announcement dates.
- State laws can differ. Several states have mini-WARN laws with lower thresholds or different counting rules, so a layoff that escapes the federal rule may still trigger a state notice requirement.
Why the rule matters in the current data
The rule is not theoretical. Layoff Atlas currently tracks 704 WARN notices covering 66,156 reported workers in its 90-day window, with 33 counts unavailable, updated October 25, 2026. Washington (17,073 workers) and California (14,224) lead the states, followed by Illinois (4,626), Texas (3,652), and Ohio (3,180). Upcoming weeks are heavy: 5,206 workers in the week starting October 25, rising to 7,781 in the week starting November 15, the heaviest week in the current window.
Those figures are reported plans, not confirmed job losses, and coverage varies by state. But they show why staggered layoffs deserve a second look: some rounds scheduled over consecutive weeks may belong to the same 90-day window at the same site, and workers in an early, small round may have been owed notice all along.
If you suspect rounds at your site should have been combined, gather the dates, headcounts, and notices for each round and compare them with your state's WARN list. An employment lawyer or your state's dislocated worker unit can assess whether the combined total crossed a threshold.
Notice is only useful if it arrives before the job ends, and a rule that let employers dodge it by laying people off a few dozen at a time would protect no one.
Data source: Layoff Atlas
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