The following rules can be considered optional.
In Taiwanese rules it is customary to apply a rule according to which a player is prohibited from going out on a tile, which he has missed during the very same turn. He must discard a tile before being able to use a missed discard again. Note that the rule is applied to a self-drawn tile, as well. in Japanese rules, where this option is common, a player is not prohibited from going out on a missed discard, if the tile is self-drawn.
E.g., if player A is calling Bamboo 3 to go out, and player B discards Bamboo 3, and player A does not claim it, he may not claim and go out on Bamboo 3, if it is discarded by player C or D on the same turn, or if he picks the tile from the Wall. Player A must make a discard before being able to claim a missed discard again.
Note however that a player can claim a missed discard, if he does not go out on that tile.
Taiwanese rules often pay an extra tai to an East winner. If the dealer goes out self-drawn, the specified bonus is paid by all losers, otherwise it is paid by the discarder alone (and just for himself, not for all losers). On the other hand, if East discards the winning tile, he must himself pay the specified bonus to the winner.
Taiwanese rules often specify an extra payment for winning a continued deal (that is, a deal where the same player continues to act as a dealer).
The rule resembles the Japanese practice of giving a bonus for winning a dealer's extra hand, but there are significant differences.
As in Japanese rules, the bonus is cumulative and increases for each successive deal. E.g., the bonus for winning the first extra hand is 2 tais. Winning the second successive extra hand earns 4 tais, and winning the third successive extra hand earns 6 tais. When East wins self-drawn, the bonus is paid by all losers, otherwise it is paid by the discarder only (but unlike the Japanese rules, not for all losers). If there are multiple winners, the discarder pays each winner as he would be the sole winner.
On the other hand, if East loses a continued deal by discarding the winning tile, he must himself pay the bonus to the winner (2 tais for the first continued deal, 4 tais for the second, etc.). If there are multiple winners, East pays each winner as he would be the sole winner.
As the deal normally does not pass after a draw, a continued deal is not necessarily a result of East having won the previous deal: accordingly, the players must agree whether drawn deals are allowed between the successive wins and whether they increase the counter for continued deals.
The etiquette for correct drawing and claiming of tiles may vary, as may the consequences for violating the etiquette. Basically the irregularities which have no effect on other players should have no consequences in friendly games. To avoid confusion, the players should agree on the etiquette and penalties before beginning the game.
In the following some common practices are listed:
Players often agree on applying insurance penalties for irresponsible discards, that is, for dangerous discards that let another player go out on a big hand (this is often called "letting off a canon").
Insurance penalties are normally applied for the following hands:
Note that letting another player rob a Kong that involves a dangerous tile is considered the same as discarding a dangerous tile, and accordingly penalized in the same way.
Claiming a dangerous discard for a Kong does not result in applying insurance penalties (since in this case a player already had that dangerous set completed as a concealed Pung – promoting this set into a melded Kong does not necessarily bring the hand any closer to winning).
Often it is agreed that a player can declare "No Choice", if he has no other choice than making a dangerous discard. In this case he must expose his hand temporarily, and he will not be penalized for making a dangerous discard.
A player who is liable for "letting off a canon" must pay for all losers (that is, not only for himself, but also for the other two players). In addition, there is no settlement among losers.