Policy designed to act as a supplement to Medicare. The supplementation is in the form of additional benefits to that provided by Medicare. The additional benefits are in the form of payment for medical expenses incurred but excluded by Medicare's deductibles, by limitations on approval medical charges, by limitations on length and type of care in nursing facilities, and by limitations imposed by various cost-sharing requirements. Most of these policies pay substantially less than 100% of the expenses not covered under Medicare. Insurance companies that sell Medigap policies are required by law to have an open enrollment period of six months for those individuals who first enroll in Medicare Part B at age 65 or older. Insurance companies can, however, exclude preexisting conditions from the data of initial coverage, but for no more than six months. Insurance companies are restricted by the National Association of Insurance Commissioners to the selling of 10 standard Medigap insurance policies. Each policy is mandated to provide a basic amount of benefits.