What does insurance write-off mean?

When you see this on your doctor or dental statement or bill, what does it mean?
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On a doctor or dental statement, it means the doctor charged $50 for the visit but the insurance only allowed $45 so the doctor wrote off the other $5. When Doctors contract with a PPO, the PPO generally has an amount they will pay for certain things. If the doctor charges more for that particular proceedure, the PPO will only pay their maximum amount. Since the doctor has agreed to bill by the PPO's price list when he became a provider for the PPO, he cannot come back and charge the patient the additional amount so he writes it off as an insurance write-off.
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