How many nonbonding electrons in the lewis structure of formaldehyde?

The chemical structure of formaldehyde ( methanal) is

H-C(=O)-H

Carbon uses all four of its bonding electrons

Hydrogen uses its one bonding electron

However, oxygen uses two of its six outer most electrons to form the double bond. Thereby leaving two (non-bonding) lone pairs ( 4 electrons) on the oxygen atom.