What is a 'waiting period' in health insurance?

A waiting period in group health insurance is the time between starting employment (or other eligibility) and when health benefits begin. Under ACA rules, employer-sponsored health plans cannot have waiting periods longer than 90 days for eligible employees. Some employers offer immediate coverage; others use the full 90 days. The waiting period is distinct from: (1) elimination period in disability insurance — the wait between disability onset and when benefits begin paying; (2) probationary period — the time during which a new condition is excluded under some older policies (now banned under ACA in individual/small group). Understanding waiting periods is important when timing job changes — coverage gaps can leave significant exposure.