I am not 100% sure on this, but I believe u lose points if task is dumped after it is started..however, if task is dumped before it is started (dumping because it's score is too low), u do not lose points.
If you dump a task after accepting it (red trashcan), you lose the task and the potential points it could bring. If as an elder, co-leader or leader you dump a task directly from the board (blue trashcan), you won‘t lose points for the final race score that determines your position in the current race. If you are in Gold League, any task you dump will count against your Global Leaderboard Score.