As I understand the law, once you are late, you are assessed a penalty of 10% per full 12 month period. I am unaware of any way to "undo" that late enrollment penalty. The penalty does not apply if you receive insurance from an employer or, as you indicate from a spouse, so suspending your Medicare B coverage for your spouse's insurance coverage may restart the clock, but I am unaware of the regulations that would permit that to occur. You might contact your local SSA office and ask that question.
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