I have a bill submitted to pay a portion not paid by medicare. The bill shows what was charged, what was paid by medicare, what was paid by the secondary insurance company, and a note that lists the CPT code, and then CO45 CHGS EXCEEDS CONTRACTED FEE.
I assume this is on the secondary insurance Explanation of Benefits. The C045 typically means the charge submitted is greater than the Medicare or secondary insurance contracted amount. The amount above the Medicare contracted amount and secondary payment is either the patient responsibility or is written off depending on the secondary contracted coverage, policy limits, co-pays etc.
You might also call your secondary insurance provider and ask for details on what they cover if you are unsure - secondary coverage can sometimes be very confusing.