If we are judged individually at death, why are we all to be judged again at the last day? God must already know.

The Catholic Answers

God does not judge in order to discern guilt. At the particular judgment, which takes place as individuals die, God apportions to each soul relative remuneration or retribution. But at the end of the world, all souls will be re-united to their bodies, the souls of the just not losing their happiness, the souls of the lost not escaping their misery. The general judgment will then take place for the general manifestation of God’s justice. All men will then acknowledge His attributes, even those who have denied them during this earthly life. But those who availed themselves of God’s mercy will have nothing to fear on that day.

Radio Replies Volume 1 by Rev. Dr. Leslie Rumble MSC and Rev. Charles Mortimer Carty