Tenhou.net rules

The following is a translation of the rules used in Tenhou.net [1].

The rules

WIP

Start with 25000 points; Players must return 30000 points
Uma 10-20
Atozuke ari
Kuikae nashi
Kuitan ari or nashi option
Red dora ari or nashi option (1 5m, 1 5p and 1 5s)
Noten dealers lose the dealership. Known as "tenpai renchan".
Sudden death brings the game into the next wind. As soon as someone attains 30,000 points (riichi deposits are removed from players' scores), the game ends.
Sudden death must end at South 4 for tonpuusen, or by West 4 in hanchan.
Busting enforced. Scores below zero stop the game, nagative points are included in the point tally.
In all-last hands, if the dealer is winning, the game automatically stops on both dealer wins and dealer tenpai hands.
At the end of a game, points are rounded to the closest thousand, "4 down, 5 up".
At the end of the game, riichi deposits go to 1st place.
At the end of the game, if there is a tie, the tie is broken in favor of the person having the earlier dealership.
A pair of a double wind is worth 4 fu.
Winning with the rinshan tsumo tile is worth 2 fu.
No 2 han minimum rule. Hands always require a 1 han yaku or better.
Abortive draws (Nine terminals abortion, four riichi calls, three ron calls, four kans (separate), four same wind discards) allowed. All count as renchan.
Nine terminals abortion requires 9 or more different terminals, on the first turn before any pon, kan, chii calls or ankan formed.
Nagashi mangan allowed. Tenpai payments are replaced by the mangan payment. Dealer tenpai counts as renchan.
Double rons allowed. Repeats and deposits go to the next closest player.
Double rons occuring with the dealer winning are counted as renchan.
Pao is enforced on daisangen and daisuushi. Multiple yakuman still count. Tsumo win = responsible player pays all, ron win = responsible player pays half. Related repeats also paid through pao.
No pao on suukantsu.
Keishiki tenpai ari. Your tenpai may include a wait for a "5th tile" (however, this does not include the case when the 4 available tiles for said wait are included in your hand).
You need at least 1000 points and a next turn to pick (4 or more tiles in the wall) to declare riichi.
If the tile that was used to declare riichi is won off, the deposit is returned to the owner. //リーチ宣言牌で放銃した場合は供託料は発生しない
Furiten riichi allowed.
After riichi, letting a winning tile pass makes your hand furiten.
リーチ後の縛りをクリアしない和了型になる牌は常に見逃し、以降振聴
Ankan that changes the wait tiles after a riichi is prohibited. Okuri-kans are not allowed. Ankans that do not change your wait are allowed.
Kan dora and kan ura dora allowed.
Kan dora are flipped as follows: from ankan immediately, from minkan and from kakan are shown after discarding or picking a new replacement tile.
純正巡消しは発声＆和了打診後（加槓のみ)、嶺上ツモの前（連続する加槓の２回目には一発は付かない）
同一巡内の選択ロン和了なし(加槓牌を含む)
同巡振聴の解消は打牌時、逆巡副露では解消しない。
The last tile discarded cannot be called.
Paarenchan, renhou, sanrenkou, iisou sanjun, shiisan puta, etc. nashi.

External links

Tenhou manual page (Japanese)