Question: Is paying double if you roll doubles a house rule or a National Mah Jongg League Rule?

Answer: Paying double to a winner is a House Rule. So, if East rolls a double at the beginning of their turn, the dice or a doubles tile marker is placed on the top of the player’s rack as a reminder that doubles were rolled. At the end of the game, all payouts are doubled. As an example, If, on a .25 hand, someone picked their own Mah Jongg and made it without Jokers, instead of the payout being $1.00, the payout would be $2.00.

See also ID53, The League on House Rules.