Illegal moves

1. Not following the touch-move rule: If you touch one of your pieces with the intention to move it, you must make that move if it's possible. If you touch your opponent's piece, you have to capture it if it's possible.

2. Illegal Castling: You can't castle in certain situations:

• If your king has already moved.

• If the rook you want to castle with has already moved.

• If the squares between your king and the rook are occupied.

• If your king is in check.

• If your king would pass through or end up on an attacked square.

3. Putting Your King in Check: Making a move that would put your own king in check is not allowed.

4. Illegal En Passant: En passant is only allowed if your opponent's pawn moves two squares forward from its starting position and lands next to one of your pawns. You can only do this where it's allowed. Otherwise, it's an illegal move.

5. Breaking Time Control Rules: Playing after the time has run out or not making the required number of moves within the given time is illegal.

​

If you make an unauthorized move during a game, your opponent or the referee can let you know. You'll have to take back that move and make a legal one instead. Sometimes, there are penalties like giving your opponent more time or losing the game, depending on the tournament rules and the seriousness of the mistake.

​

​