I have a provider that has recently opened his own practice. He is seeing several previous patients that has been billed the 99203 within the past 3 years. However, with them being seen in a new practice we billed 99203 as they being seen in a new practice with a new NPI number. The claims are being returned stating we can only bill 99203 once every 3 years. Is there a modifier or a more appropriate that code should be used?