At every round, every year, someone always wants to keep the scores on a separate scorecard and transfer the scores over to the tournament cards after the round. I have always refused to be a part of this as I am quite capable of marking my playing partner’s score correctly on the tournament card. If I do make a mistake, I always have the eraser and can change my work. I have never gotten the whole scoring on a card separate than the official tournament card and I don’t play in any other tournaments where this is a common practice.
The best advice I can give to anyone about scorecards, is ALWAYS turn in your own scorecard and hand over the card that you scored to the player you scored. Do not rely on anyone else to turn in your card.