The dipole moment is shown with an arrow in the Lewis structure. The ionic character of the $CO$ bond is ~ 25%.
Work Step by Step
The electronegativity of $C$ is 2.5, and the electronegativity of $O$ is 3.5. The electronegativity difference is 1. Referring to Figure 9.10, we see that this is a nearly 25% ionic character for the bond. The Lewis structure is shown in the attached image.