When Patient Has Three Insurance Plans - Primary, Secondary, and a Third (Tertiary)

by Louise
(Asheville, NC, USA)

My client has Medicare primary, a Medicare supplement and then a third insurer. How do I file for that third reimbursement?


I know most of us dread these kinds of scenarios where you have three different insurance payers - and one of them is usually Medicare.

The third claim is called a Tertiary claim. Tertiary is defined as third in the order of level.

From our experience the third (tertiary) claim is filed after the primary and secondary claims have been successfully processed. The tertiary insurance ID should be in block 1a of the CMS-1500 form. The primary insurance information should then be in boxes 9a and 9d. Explanation of Benefits (EOB's) from both the primary and secondary insurance plans should be attached to the CMS-1500 form. We've only filed tertiary claims by paper CMS-1500 but haven't filed electronically yet.

For those visitors unfamiliar with having a third insurance plan, a claim can be submitted for the remaining balance that the primary and secondary insurance didn't cover. We've only sent tertiary claims by paper CMS-1500 form. It must have the EOB's from both the primary and secondary insurance payers attached to be successfully processed.

The primary claim is filed first either electronically or on a paper CMS-1500 form. Once the primary insurance pays the provider, the secondary insurance claim is filed. For the secondary claim - whether filed electronically or CMS-1500 form - must have information from the primary explanation of benefits (EOB) entered on the claim. When submitted by paper form, the secondary must have a copy of the EOB attached.

Anytime you send a paper attachment with the CMS-1500 claim form, it's very important to make sure any attached EOB's are good quality copies and all the important information can be easily read. Many of these are scanned in by the insurance company which usually further degrades the quality of the copy. We learned this lesson the hard way after having a few secondary and tertiary claims rejected because of a poor quality (or too light) EOB. When a claim is rejected for something like this, it creates a lot of work for us the finding the original EOB(s), re-copying, and then resubmitting the claim.

There can be many scenarios when a patient is covered by three insurance plans and figuring out which is primary, secondary, and tertiary can be confusing to say the least. Determining who is primary and secondary can depend on several variables: if the patient married, is employed or retired, has a working spouse and is on their employer's plan, etc.

Generally, if a patient is working and covered by their employer's health insurance plan, that insurance is considered primary. If the patient is retired and covered under their spouse's insurance plan, the primary would be the spouse's insurance and Medicare would be secondary.

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