A waiting period is the time between when your insurance policy becomes effective and when certain benefits become available. Waiting periods are common in guaranteed-issue plans and conversion plans, where the insurer cannot ask medical questions. They protect the insurer from adverse selection — people signing up only because they need immediate treatment. Waiting periods vary by plan and by benefit. In the plans we compare, basic dental care usually waits about 3 months (some plans have none), while major dental work and orthodontics wait anywhere from 6 months to 2 years — and a few plans phase coverage in over the first years instead. Some plans also limit coverage for pre-existing conditions at first. Always check the specific plan's waiting periods before you rely on a benefit. Conversion plans that are exercised within the conversion window may have reduced or eliminated waiting periods for pre-existing conditions.