What notices are required before an employee is terminated or laid off?

Short Answer: Advance notice is required for mass layoffs under the WARN Act, but it is not necessary for individual terminations.

Full Answer: Federal law does not require advance notice for individual terminations unless specified in an employment contract or collective bargaining agreement.
However, under the Worker Adjustment and Retraining Notification (WARN) Act, employers with 100 or more employees must provide at least 60 days written notice before mass layoffs or plant closings affecting 50 or more employees at a single site.
Some states have mini-WARN laws with stricter requirements or lower thresholds. Employers must also comply with state-specific termination notice requirements, such as final paycheck timing and information on unemployment benefits.

General Federal Standard: The WARN Act requires 60 days' notice for mass layoffs but not for individual terminations.

Link to a legislative resource from trusted sources: U.S. Department of Labor - WARN Act Compliance