From IBC November 2013:

We are writing to let you know that we will be contacting your group customers to communicate the Medicare Exclusion and application of this exclusion to their benefit plan.

What is the Medicare Exclusion?
The Medicare Exclusion applies to members for whom Medicare would be the primary payer but they have not elected to enroll. These members will be responsible for paying their doctor, hospital, or other medical professional the amount Medicare would have paid and any applicable copayments, coinsurance, and deductibles. In turn, their group health benefit plan will only pay the remaining balance on claims submitted as if the member had enrolled in Medicare Parts A and B.

We will also be contacting these members to inform them of the Medicare Exclusion and the steps they need to take to maximize their health plan benefits and minimize their expenses by enrolling in Medicare. If you have any questions, please contact your Independence Blue Cross Account Executive.

Click the links below to see the notices/letters: