A COCC is a Certificate of Creditable Coverage. This is the proof that you need to provide when you change carriers to prove that you had coverage. When you leave employment, or your employer changes carriers, a child or spouse drops off coverage, you will receive a COCC. It is very important for you to hold on to this document for a period of 18 months. When you change group/employer sponsored health carriers, the law mandates that your new carrier provide credit for your preexisting conditions if you have had continuous coverage for the past 18 months or more. Many individual plan carriers provide the same credit if you have prior, uninterrupted coverage.
If you are changing individual coverage, a certificate of creditable coverage is not issued. Even so, group and individual carriers frequently offer credit for preexisting conditions if you had prior coverage. Bottom line on this subject is to keep a good record of who was covered, during what periods of time.