Yes. I get asked this question all the time from individuals who are still working and do not want to start their Social Security benefits just yet. If you are covered under your employers insurance policy and have determined that it is more cost effective to enroll into Medicare, then you will need to obtain a creditable coverage letter for your late Medicare Part B and Medicare Part D enrollment. This letter which must be provided by your employer, tells Medicare that you were covered by Group health insurance during the time that you were originally eligible for Medicare. As long as the insurance was creditable, you will not receive any late enrollment penalties. Since you do not want to start your Social Security yet, Medicare can bill you for the cost of your Part B coverage rather than deducting it from your Social Security. You do not have to start your Social Security in order to start your Medicare benefits. They are two separate benefits.
Please note it is important to review your Group Health Insurance benefits before disenrolling and switching to Medicare. Some Group Health benefits offer additional services not covered by Medicare so its important to review your evidence of coverage and make sure the change is right for you. Many individuals have saved a considerable amount of money switching to a Medicare Plan and feel that the savings far outweigh any change in benefits.