Penalties

Some of us are a little anal and make sure their i's are dotted and their t's are crossed. Others don't. They will probably end up with a penalty of some sort.
Penalties-
Part A Late Enrollment Penalty-
Some people have to buy Part A because they 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 go up 10%. You'll have to pay the higher premium for twice the number of years you didn't sign up. Most people have worked and paid into Social Security long enough (40 Quarters)where they'll get Part A for free.
Part B Late Enrollment Penalty-
If you didn't get Part B when you're first eligible, your monthly premium may go up 10% for each 12-month period you could've had Part B, but didn't sign up. In most cases, you'll have to pay this penalty each time you pay your premiums, for as long as you have Part B. And, the penalty increases the longer you go without Part B coverage. Usually, you don't pay a late enrollment penalty if you meet certain conditions that allow you to sign up for Part B during a Special Enrollment Period. 
For Example: You continue to work and your Employer has over 20 employees, you would not be required to sign up for Part B. If there are under 20 employees then you would have to sign up.
Part D Late Enrollment Penalty-
The late enrollment penalty is an amount that's permanently added to your Medicare drug coverage (Part D) premium. You may owe a late enrollment penalty if at any time after your Initial Enrollment Period is over, there's a period of 63 or more days in a row when you don't have Medicare drug coverage or other creditable prescription drug coverage . You’ll generally have to pay the penalty for as long as you have Medicare drug coverage.
How do they Calculate the Penalty-
The cost of the late enrollment penalty depends on how long you went without Part D or creditable prescription drug coverage. Medicare calculates the penalty by multiplying 1% of the "national base beneficiary premium" ($33.06 in 2021) times the number of full, uncovered months you didn't have Part D or creditable coverage. The monthly premium is rounded to the nearest $.10 and added to your monthly Part D premium. The national base beneficiary premium may change each year, so your penalty amount may also change each year. Yikes!

Some people blow off Part D because they don't take Meds. Pretty silly considering they can probably get a Medicare Advantage Plan that includes Part D for a $00.00 per month.

Talk to your Medicare Advisor.