The formal charge on carbon atom in the octet Lewis structure of CO is

Lewis structure of CO is

Or

F C on carbon = $4-2-\frac{1}{2}\left(6\right)=-1$

F C on oxygen = $6-2-\frac{1}{2}\left(6\right)=+1$

$\mathrm{F}\mathrm{C}=\left[\begin{array}{l}\mathrm{Total}\text{ number}\\ \text{ of valence }\\ \text{electrons}\\ \text{ in the free atom}\end{array}\right]-\left[\begin{array}{l}\text{Total number}\\ \text{ of non bonding}\\ \text{ electron}\end{array}\right]-\frac{1}{2}\left[\begin{array}{l}\mathrm{T}\text{otal number}\\ \text{ of bonding}\\ \text{ electrons}\end{array}\right]$