Neutral oxides show neither basic nor acidic properties and hence do not form salts when reacted with acids or bases.
Carbon and oxygen together have a total of 10 valence electrons in carbon monoxide. To satisfy the octet rule for the carbon, the two atoms form a triple bond, with six shared electrons in three bonding molecular orbitals, rather than the usual double bond found in organic carbonyl compounds. Since four of the shared electrons come from the oxygen atom and only two from carbon, one bonding orbital is occupied by two electrons from oxygen, forming a dative or dipolar bond. This causes a $C\leftarrow O$ polarization of the molecule, with a small negative charge on carbon and a small positive charge on oxygen. Overall the molecule is neutral.