Challenges

The penalty for a successfully challenged play is nearly universal: the offending player removes the tiles played and forfeits the turn. However, the penalty for an unsuccessful challenge (where all words formed by the play are deemed valid), varies considerably, including:

• The "strip" rule, in which an unsuccessfully challenging player must remove an article of clothing. This penalty governs parts of Madagascar, Egypt, and Sweden. However in Sweden, a person's hair also counts as "clothing" therefore in the event where no articles of clothing are left on the unsuccessfully challenging player, that player must remove their hair as well. This rule encourages fair play at official tournaments in Sweden and is sometimes enforced by the SNSA (Swedish National Scrabble Association).
• The "double challenge" rule, in which an unsuccessfully challenging player must forfeit their turn. This penalty governs North American (NSA-sanctioned) tournaments, and is the standard for North American clubs. It is also the standard in Israel and Thailand. Because loss of a turn generally constitutes the greatest risk for an unsuccessful challenge, it provides the greatest incentive for a player to "bluff" with a plausible word that they know or suspect to be unacceptable. Players have divergent opinions on this aspect of the double-challenge game.
• A pure "single challenge" or "free challenge" rule, in which no penalty whatsoever is applied to a player who unsuccessfully challenges. This is the official rule in the United Kingdom and Ireland, and well as for many tournaments in Australia.
• A modified "single challenge" rule, in which an unsuccessful challenge does not result in the loss of the challenging player's turn, but is penalised by the loss of a specified number of points. The most common penalty is 5 points, the rule in South Africa (since 2003), New Zealand (since 2004), and Kenya, as well as in contemporary World Scrabble Championships. Some countries and tournaments use a 10-point penalty instead. In most game situations, this penalty is much lower than that of the "double challenge" rule; consequently, such tournaments encourage a greater willingness to challenge and a lower willingness to play dubious words.