While some types of insurance, such as auto, upon purchase, can take immediate effect, this does not hold true of health insurance. Before coverage can start, your application must be underwritten, and of course the insurance provider must approve of the application. In some cases, coverage can only begin on a specified date, such as the first of the month. Other companies may allow you during the application process to choose your own date on which the plan will go into effect. However, keep in mind that your insurance is not active until you have received the policy in the mail from your insurance provider.