Many travel insurance policies require purchase of travel insurance on the date prior to departure or earlier.  A few insurance carriers will allow you to purchase on your departure date. However, the policy does not go into effect until the day following purchase.  Additionally, certain benefits are dependent upon when the insurance is purchased.  In order to be eligible for a pre-existing exclusions waiver, be covered for financial default or purchase optional upgrades such as cancel for work or cancel for any reason, purchase must be made within 14 - 21 days of your first deposit, depending on the policy.