How long can a former employee continue COBRA coverage after leaving their job voluntarily?

Under COBRA (Consolidated Omnibus Budget Reconciliation Act), employees who voluntarily leave their job, are laid off (except for gross misconduct), or have their hours reduced can continue group health coverage for up to 18 months. Qualifying events for 36-month continuation: death of the covered employee; divorce; employee becomes eligible for Medicare; dependent child aging off the plan. COBRA coverage is identical to the employer's plan but the former employee pays the full premium (employer share + employee share) plus up to 2% administrative fee — making it expensive.