9(a) It having been decided which side is to have the first service, the player in the right-hand service court of that side commences the game by serving to the player in the service court diagonally opposite. If the latter player returns the shuttle before it touches the ground, it is to be returned by one of the "In" side, and then returned by one of the "Out" side, and so on, till a fault is made or the shuttle ceases to be "in play" (vide paragraph (b)). If a fault is made by the "In" side its right to continue serving is lost, as only one player on the side beginning a game is entitled to do so (vide Law 11), and the opponent in the right-hand service court then becomes the server; but if the service is not returned, or the fault is made by the "Out" side, the "In" side scores a point. The "In" side players then change from one service court to the other, the service now being from the left-hand service court to the player in the service court diagonally opposite. So long as a side remains "In", service is delivered alternately from each service court into the one diagonally opposite, the change being made by the "In" side when, and only when, a point is added to its score.
9(b) The first service of a side in each innings shall be made from the right-hand service court. A "Service" is delivered as soon as the shuttle is struck by the server・s racket. The shuttle is thereafter "in play" until it touches the ground, or until a fault or "let" occurs, or except as provided in Law 18. After the service is delivered the server and the player served to may take up any positions they choose on their side of the net, irrespective of boundary lines.
The player served to may alone receive the service, but should the shuttle touch, or be struck by, his partner the "In" side scores a point. No player may receive two consecutive services in the same game, except as provided in Law 12.
Only one player of the side beginning a game shall be entitled to serve in its first innings. In all subsequent innings each partner shall have the right, and they shall serve consecutively. The side winning a game shall always serve first in the next game, but either of the losers may receive the service.
If a player serves out of turn, or from the wrong service court (owing to a mistake as to the service court from which service is at the time being in order), and his side wins the rally, it shall be a "Let", provided that such "Let" be claimed and allowed, or ordered by the umpire, before the next succeeding service is delivered.
If a player of the "Out" side standing in the wrong service court is prepared to receive the service when it is delivered, and his side wins the rally, the mistake shall stand and the players・ positions shall not be corrected.
Should a player inadvertently change sides when he should not do so, and the mistake not be discovered until after the next succeeding service has been delivered, the mistake shall stand, and a "Let" cannot be claimed or allowed, and the players・ position shall not be corrected.
13. Single Play
In singles, Laws 9 to 12 hold good except that:
13(a) The players shall serve from and receive service in their respective right-hand service courts only when the server・s score is 0 or an even number of points in the game, the service being delivered from and received in their respective left-hand service courts when the server・s score is an odd number of points. Setting does not affect this sequence.13(b) Both players shall change service courts after each point has been scored.