Illegal move

A move is illegal when it fails the movement rules or exposes your king to check, for instance moving a pinned piece or stepping a king onto an attacked square. A move is treated as completed once the player presses the clock. If an illegal move is found afterwards, the position before it is restored and the player must make a legal move with the same touched piece if possible, under touch-move. The first completed illegal move gives your opponent two extra minutes. The second completed illegal move by the same player loses the game, unless the opponent has no possible way to mate, in which case the game is drawn. Some mistakes are handled as illegal moves too: pressing the clock without moving, using two hands for one move and pressing, and reaching the last rank with a pawn without replacing it, in which case the pawn becomes a queen. Rapid and blitz have their own versions. The penalty is one minute rather than two, and in games without an arbiter watching, the opponent must claim before making their next move. Online boards simply refuse illegal moves, so over-the-board play is where the habit of checking every move matters.

Also worth reading is Check. Check is the state of a king that stands attacked by one or more opposing pieces; the player whose king it is must end the attack with the very next move, because no legal move may leave one's own king attacked.

Also worth reading is Adjusting a piece. Adjusting a piece means straightening one on its square; the Laws allow it only to the player on the move, who must first say "j'adoube" or "I adjust" to show they do not intend to move it.

A neighboring idea is Chess clock. A chess clock is a pair of linked timers of which only one runs at a time; after each move a player presses their side to stop their own time and start the opponent's.

Once "Illegal move" is familiar, the next question is what to work on at your rating, which the improvement plans by rating band answer with game and puzzle data.

Related terms

• Touch-move rule

  Touch-move is the over-the-board rule that binds a player to a piece once it has been deliberately touched: your own piece has to be moved and an opponent's piece has to be captured, wherever a legal move exists.

• Check

  Check is the state of a king that stands attacked by one or more opposing pieces; the player whose king it is must end the attack with the very next move, because no legal move may leave one's own king attacked.

• Promotion

  Promotion is the compulsory change of a pawn that reaches the last rank into a queen, rook, bishop or knight of its own color, made as part of the same move and chosen freely, whatever has been captured so far.

• Arbiter

  The arbiter is the official who sees that the Laws of Chess and the rules of the event are followed, rules on disputes and claims, and can penalize rule breaches during a tournament.

• Chess clock

  A chess clock is a pair of linked timers of which only one runs at a time; after each move a player presses their side to stop their own time and start the opponent's.

• Forfeit

  A forfeit is a loss awarded without a finished game, for example when a player arrives after the default time, persistently refuses to follow the Laws, or has an unapproved electronic device in the playing venue.

Guides that go further

• How to choose a chess coach

  What to decide first, the questions to ask, what a first lesson should show and the red flags to avoid.

• How much does chess coaching cost?

  Published rates for private, group and subscription chess coaching, with the source and the date of each.

• The first lesson

  A game review, a read on your level and a written study plan from George Li.

Sources

• FIDE Laws of Chess (effective 1 January 2023), Articles 3.9.2 and 3.10, read Oct 21, 2026.
• FIDE Laws of Chess (effective 1 January 2023), Articles 7.5.1 to 7.5.5, read Oct 21, 2026.
• FIDE Laws of Chess (effective 1 January 2023), Appendix A.3 and A.5.2, read Oct 21, 2026.