The effective date is the date on which your insurance coverage officially begins. Claims for services received before the effective date will not be covered. For underwritten plans, the effective date is typically the first of the month following approval of your application. For plans for people leaving a group plan, the start date depends on the plan — some let you choose a date right after group coverage ends, others start on the first of a month after you apply or are accepted — so check it to avoid a gap. Some insurers allow you to choose an effective date within a specific window. If your plan has waiting periods, those periods begin counting from the effective date. It is important to know your exact effective date so you can schedule treatments and fill prescriptions accordingly. Your effective date also determines your policy anniversary date, which is when your plan renews each year.