I am 65 and retired, but still have my insurance from my former employer for the remainder of the year because of the ACA look back period. I want to hold off signing up for Medicare until open enrollment later this year. Will I have to pay the penalty on my premiums if I wait?
You have only 3 months...including the month you turn 65 to do this. After that, you will pay the higher premium for the rest of your life. Just how high? Depends on how long you wait.
Go to the Medicare.gov website...there you can see the calculations.
As for ACA look back? What? The only "look back" I have ever heard of is that you must have some insurance each year to avoid the penality. But...once you change over to Medicare, ,you coverage would be continuous...you drop one when you start the next. All of which is permissible because of a "life changing event".