When you create a claim in Therabill to Medicare, you may notice that the right hand side of the claim form (Box 4, Box 7 with NONE entered in to Box 11). Many people mistakenly think that this should be filled with the insured's Medicare information (as it is with most commercial insurance claims). For Medicare claims, the Medicare recipient information is not filled in to these boxes on the CMS-1500. According to the CMS guidelines for filling out the CMS-1500, this section of the CMS-1500 should be filled out with policy information of any insurance policy that the patient has that is primary to Medicare. If the patient does not have insurance that is primary to Medicare, these boxes should be left blank and have NONE entered in Box 11. If the patient does have insurance primary to Medicare, then the insurance policy information of the primary is filled into these boxes.
Box 9 on the CMS-1500 (which for commercial insurance claims holds secondary payer information) should only include Medigap information when submitting a claim to Medicare.
At the time of this writing, here is a valid link to the CMS guidelines. If this link is broken, you can find the guidelines by doing a Google Search for the keywords "CMS instructions Chapter 26".