Medicare beneficiaries who were eligible for but did not enroll in a Part D when they were first eligible and later want to enroll, pay a late-enrollment penalty, basically a premium surtax, if they did not have acceptable coverage through another source such as an employer or the U.S. Veterans Administration. This penalty is equal to 1% of the national premium index times the number of full calendar months that they were eligible for but not enrolled in Part D and did not have creditable coverage through another source. The penalty raises the premium of Part D for beneficiaries, when and if they elect coverage.