The Worker Adjustment and Retraining Notification (WARN) Act requires US employers of 100+ workers to give 60 calendar days' written notice before a "plant closing" or "mass layoff." The Department of Labor describes it as a notice obligation, not a substantive layoff restriction. In practice, the 60-day window and the cash impact of getting it wrong make WARN one of the most consequential US employment laws for any growth-stage company.
The triggers
WARN triggers in two scenarios:
- Plant closing — permanent or temporary shutdown of a single employment site, or one or more operating units within a site, that results in employment loss for 50+ full-time employees during any 30-day period
- Mass layoff — reduction in force at a single site that affects 500+ employees, OR 50-499 employees where they constitute at least 33% of the active workforce
"Employment loss" includes termination, layoff exceeding 6 months, or reduction in hours exceeding 50% for 6 months. "Single site of employment" generally means a geographically separate location, though remote-worker case law is still evolving.
State mini-WARN acts
Sixteen states have stricter versions of WARN. California's CAL-WARN applies at 75 employees rather than 100, with no part-time exclusion. New York's WARN applies at 50, with a 90-day notice requirement instead of 60. New Jersey's amended WARN requires one week of severance per year of service in addition to notice. DOL's state-contact list is the best entry point for state-by-state rules.
Who gets the notice
WARN notice must go to:
- The affected workers (or their union representative if covered by a CBA)
- The state's dislocated worker unit
- The chief elected official of the local government where the employment site is located
The notice must contain specific elements — expected termination date, whether it is permanent or temporary, the bumping-rights status, and a contact person.
The "unforeseeable business circumstances" exception
WARN allows shorter notice in three narrow scenarios: faltering company (only for plant closings, not mass layoffs), unforeseeable business circumstances, and natural disaster. The 2020 pandemic generated a wave of WARN class actions on the "unforeseeable" defence; courts split on whether economic downturn alone qualifies. The safest read in 2026: the exception is genuinely narrow and should be invoked only with counsel.
Plan rather than react
Three operational moves reduce WARN exposure:
- Maintain a current headcount by site (including remote workers assigned to a site)
- Build the WARN-trigger threshold into scenario planning before any RIF is announced
- Distinguish hard terminations from hours-reduction cases in workforce planning models — both count toward triggers
See our WARN Act glossary entry for definitions and the RIF/layoffs glossary entry for the procedural runbook. For broader severance design, the total compensation mapping matters because state mini-WARN severance attaches to base pay only.