When Can You Swap?
You can use your turn to swap tiles during the game as long as there are at least seven tiles remaining in the bag. When you want to exchange your tiles, you must announce how many tiles you want to swap, place the tiles face down on the table (unless you announce that you are exchanging all seven of your tiles), start the opponent's timer, draw your new tiles and then put the old tiles back into the bag.
Disputes
If the number of tiles to be swapped differs from the number of tiles placed face down on the board, the number of tiles placed face down are exchanged. For example, if you announce you will exchange five tiles but only place four on the table, you can only swap those four placed on the table. You are not penalized for putting the tiles that you wish to swap back into the bag before selecting your new tiles. However, you do not get to pick over if you receive those same tiles when you draw your new tiles.
Penalties
If you announce that you are going to swap your tiles but do not announce how many tiles you are going to swap nor do you place a tile or tiles face down on the table, you lose your turn and are not permitted to swap any of your tiles.
If you swap tiles when there are less than seven tiles remaining in the bag, the penalty depends on when the error is discovered. If you realize you cannot swap after you have announced an exchange but before you exchanged any tiles, your turn is considered a pass. If you have drawn new tiles but the tiles have not been placed on your rack and the old tiles have not been added to the bag, everyone gets to see the new tiles and then the new tiles are placed back in the bag and your turn is a pass. If you have already returned the old tiles to the bag but have not yet placed the new tiles on your rack, your opponent can look at the new tiles, all tiles in the bag and any two tiles that you kept and choose which tiles to give you within 60 seconds. Unused tiles are placed back in the bag. If you have started to put the new tiles on your rack, your opponent gets to see the number of tiles you exchanged plus two (up to seven) tiles from your rack and from those tiles and the tiles in the bag, choose which tiles to give you. For example, if you had seven tiles and exchanged four, your opponent would get to look at six tiles from your rack and, from those six and any remaining tiles in the bag, choose which six you would keep. If the exchange is noticed after your opponent has completed her turn, you lose 30 points from your score.