There are two cases:

1.If the reflect light is from the Infrared light, please turn off the infrared of camera ,
add a white light for supplement ,all the infrared cameras are not recommended for license plate ,it will not able to see the plate clear with a infrared light.

2,If the reflect light is from car lamp, please adjust the installation angle of camera,avoid the direct light from coming car lamp, or you could choose a camera with strong light suppression fucntion.