The Laws of Duplicate Bridge 4

Law 13
Incorrect Number of Cards
When the Director determines that one or more hands in a board contained an incorrect number of cards and a player with an incorrect hand has made a 'call', then when the Director deems that the deal can be corrected and played, the 'call' stands. However, at the end of play the Director may award an adjusted score. Note that a 'call' includes a pass.

If play cannot be continued then the Director will award an adjusted score and may penalise an offender.

If no call has been made the Director will correct the discrepancy and if no player will have seen another's card, play can continue normally.

When the Director determines that one or more pockets of the board contained an incorrect number of cards and a player has seen one or more cards of another players hand, the Director acts as follows:

1. If the unauthorised information is unlikely to interfere with the bidding or play, the Director allows the board to be played. If the Director then considers the information has affected the outcome the Director shall adjust the score and may penalise an offender.
2. If the unauthorised information gained is of sufficient importance to interfere with normal bidding or play Director shall adjust the score and may penalise an offender.

If it is determined after play ends that a players hand started with more than 13 cards with another player holding fewer, the result will be cancelled and an adjusted score awarded. Any offending contestant is liable to a procedural penalty.

When under this Law the Director requires play to continue, knowledge of the placement or movement of a card by the Director is unauthorised information for the partner of a player whose hand contained an incorrect number of cards.

Any surplus card, not part of the deal, is removed if found. If such a card is found to have been played to completed trick an adjusted score may be awarded.