You will need to sign up for Medicare coverage during your Initial Enrollment Period unless there is other coverage that’s similar in value to Medicare (like from an employer). If not, you may have to pay an extra recurring amount, called a late enrollment penalty.

Late enrollment penalties:

• Are recurring and permanent
• Are added to your monthly premium
• The amount is determined by how long you go without coverage
• The penalty lasts as long as you have the coverage and can be a lifetime
• Part A penalties are different

Part A late enrollment penalties:

• You may have to buy Part A if you don’t qualify for premium-free Part A
• If you have to buy Part A, and you don’t buy it when you’re first eligible for Medicare, your monthly premium may increase by 10%
• Penalties are charged for twice the number of years you didn’t sign up

Part D late enrollment penalties:

• Generally, you won’t have to pay a Part D penalty if:
  • You have credible or similar in value to Part D drug coverage
  • You qualify for Extra Help
• You’ll pay an extra 12% annually if you:
  • You don’t join a Medicare drug plan when you first get Medicare
  • You go 63 days or more without credible drug coverage
  • You may also pay a higher premium depending on your income
  • After joining a Medicare drug plan, the plan will tell you if you have to pay a penalty and what your premium will be

Source: Medicare.gov
Learn more at https://www.medicare.gov/basics/costs/medicare-costs/avoid-penalties