Editing Rules of chess (section)

====Illegal move====
An illegal move{{sfn|FIDE|2023|loc=article 3.10.2}} is a move not made according to a piece's possible defined movements{{Sfn|FIDE|2023|loc=articles 3.2 to 3.8}} or made according to its possible movements but such that its own king is left or placed in check.{{sfn|FIDE|2023|loc=article 3.9}} Furthermore, pressing the clock without making a move or making a move with two hands is considered and penalized as an illegal move.{{sfn|FIDE|2023|loc=articles 7.5.3 and 7.5.4}}

A player who makes an {{chessgloss|illegal move}} must retract that move and make a legal move. That move must be made with the same piece if possible, because the touch-move rule applies. If the illegal move was an attempt to castle, the touch-move rule applies to the king but not to the rook. If the mistake is noticed, the game should be restarted from the position in which the error occurred.{{sfn|FIDE|2023|loc=article 7.5.1}} The arbiter should adjust the time on the clock according to the best evidence.{{sfn|FIDE|2023|loc=article 7.1}} Some regional organizations have different rules.{{efn|The USCF requires that only an illegal move within the last ten moves be corrected. If the illegal move was more than ten moves ago, the game continues.{{sfn|Just|2019|loc=chapter 1, section 11B}}}}

A player may correct an illegal move if the player has not pressed the clock. In standard chess, if a move is found during the game, the position immediately before the irregularity is reinstated.{{sfn|FIDE|2023|loc=article 7.5.1}} In the most used form of rapid chess and blitz chess if the move is found before the opponent moves, the position immediately before the irregularity is also reinstated.{{sfn|FIDE|2023|loc=appendices A.5.2 and B.3}}{{efn|If the player has pressed the clock, the standard USCF rule is that two minutes are added to the opponent's clock.}}

According to the FIDE Laws of Chess, the first stated completed illegal move results in a time penalty. The time penalty consists of giving the opponent two minutes extra time in standard chess,{{sfn|FIDE|2023|loc=article 7.5.5}} or one minute extra time in rapid or blitz.<ref>{{Cite web |date=2023-04-05 |title=Updated FIDE Laws of Chess – Suffolk Chess |url=https://suffolkchess.org/2023/04/updated-fide-laws-of-chess.html |access-date=2024-02-10 |language=en-US |quote=Previously for an illegal move in Rapidplay the opponent would receive 2 extra minutes. This has now changed to 1 minute, the same as in Blitz. |archive-date=2023-09-22 |archive-url=https://web.archive.org/web/20230922015453/https://suffolkchess.org/2023/04/updated-fide-laws-of-chess.html |url-status=live }}</ref> The second stated completed illegal move by the same player results in the loss of the game,{{sfn|FIDE|2023|loc=article 7.5.5}} unless the position is such that it is impossible for the opponent to win by any series of legal moves (e.g. if the opponent has a [[bare king]]) in which case the game is drawn.{{sfn|FIDE|2023|loc=article 6.9}} A move is completed when it has been made and the player has pressed the clock.{{sfn|FIDE|2023|loc=article 6.2.1}}

Under USCF rules, if a player completes an illegal move in blitz chess, the player's opponent may claim a win before making a move (if the opponent has enough material to win). One way to claim this win is to take a King left in check by the opponent. Once the illegal move has been answered, the move stands.{{sfn|Just|2019|loc=chapter 11, section 7d}}