Consider the following molecules:

What is the formal charge on C in CS₂ and in ${\mathrm{CO}}_3^{2-}$

Formal charge on C atom of CS₂
Formal charge on an atom in a Lewis structure
= [Total number of valence electrons in the atom] - [Total number of non-bonding or lone pair e-] - 1/2 [Total number of bonding (shared electrons)]
$=4-0-\frac{1}{2}\times 8=0$
Similarly formal charge on C atom of ${\mathrm{CO}}_3^{2-}$ is zero.