Question: When we are playing for money or points, who is responsible for tallying a player’s score? How do I know what I have to pay the winner?

Answer:  The winning player (winner) is responsible for announcing the value of their hand.  In the situation where the winning player forgets to include the value for a jokerless hand, or has stated the wrong value, and another player points it out, the winning player is paid what they initially declared.  As well, if the winner remembers after being paid that they didn’t calculate their winning value correctly, they cannot collect an additional amount or refund an overage to the other players.

Source:  Mah Jongg Made Easy 2024, page 30 para. 10