Courts and administrative agencies, including the US National Labor Relations Board, are expanding the definition of “employer” to allow liability for employment obligations to cross corporate lines. Various legal theories, including joint employer, single employer, and alter-ego theories, are being used to treat nominally separate corporate entities as one employer for liability purposes. The result of this definitional expansion is that affiliated companies are being found liable for labor and employment law violations of subsidiary or sister companies, including violations of the Worker Adjustment and Retraining Notification, Employee Retirement Income Security Act, wage and hour, discrimination, and whistleblower laws, among others. Many corporate structure forms are put at risk, including holding and operating companies, parent-subsidiary relationships, private equity management-portfolio company relationships, general and limited partnerships, independent contractor relationships, and joint ventures. This session will address the factual and legal bases for disregarding corporate separateness in the labor and employment law setting and suggest practical strategies to minimize or avoid liability.