Final answer:
Employers with over 100 employees must provide a 60-day written notice before plant closings or substantial layoffs, as stipulated by the WARN Act.
Step-by-step explanation:
In accordance with federal regulations, specifically the Worker Adjustment and Retraining Notification (WARN) Act, employers with more than 100 employees are required to provide a written notice 60 days in advance of plant closings or substantial layoffs. If a permitted facility is permanently closed or its ownership is changing, the permit holder must adhere to this mandate, as it ensures that employees have a sufficient period to prepare for the transition, be it through seeking new employment opportunities or arranging necessary personal affairs.