Our dentist has coded a restoration with 3 surface codes and a + sign and saying to bill at a 4 surface code. He says it’s for shoeing the cusp? Please advise how do I code.

Shoeing the cusp is merely shaving a projection of the masticating surface and would not be considered a fourth surface. Therefore billing for a 4 surface restoration would be incorrect. A more appropriate way of coding would be to code the three surface restoration along with D9551 occlusal adjustment for the shoeing, as long as he did not cause the projection and the need for the shoeing of the cusp due to his/her restoration.