Employers are legally required to give employees notice if the layoff will involve a large number of employees or the closing of a plant. The federal WARN Act requires employers with at least 100 employees to give 60 days' notice before a plant closing or mass layoff. If the employer doesn't give the required notice, and doesn't fit into an exception to the law's requirements, employees may be entitled to pay in lieu of notice. See Nolo's article Layoffs and Plant Closings: Know Your Rights for more information.