Erroneously delaying Medicare Part B can have significant consequences—including a lifetime premium penalty. Designed to encourage enrollment when first eligible, this late enrollment penalty is also imposed on those who simply make a mistake. For as long as they have Medicare, these individuals will pay the regular monthly Part B premium plus an additional 10 percent for each year they delayed signing up. While it is important that a penalty appropriately deter anyone who might actively seek to avoid Medicare enrollment, it must not punish those who make honest mistakes. Congress should enact policies to reduce or eliminate lifetime premium penalties for beneficiaries who were misinformed or uninformed about Medicare enrollment rules.