Medicare beneficiaries can save on their coverage by enrolling in Medicare during their seven-month initial enrollment period.  The Medicare Part B late enrollment penalty is 10% per year for each year you wait to enroll. For example, if you wait two years without credible coverage (employer group insurance), a 20% penalty could be added to your monthly premium. Medicare Part D deferment penalties can cost you an additional 1% per month. However, there are ways to defer Medicare enrollment without incurring penalties.