What score do I record if I pick up before holing out?

If you start a hole but don't hole out for a valid reason (the hole's already decided, it was conceded in match play, your partner already has a better score in Four-Ball, or you've reached net double bogey), record your most likely score or net double bogey, whichever is lower (Rule 3.3).

Most likely score = strokes taken + strokes you'd most likely need to finish + any penalty strokes:

Choose within each range based on the ball's position, the difficulty of the green and your ability.

In a format that doesn't allow picking up, such as an individual gross or net stroke-play competition, picking up gets you disqualified from the competition.