Everything about Illegal moves and Irregularities in Chess

Illegal moves are more common than you think. Even top GMs have fallen prey to it. Discover more in this guide on illegal moves and irregularities.

Everything about Illegal moves and Irregularities in Chess
Written by
Ranveer Mohite
Published on
Aug 24, 2022
Read time
5 min
Arbiters Rules FIDE

In the 2019 Tata Steel India Blitz, the elite GM Vidit Gujrathi "sacrificed" his King against GM Nakamura. It was a strange move that left Nakamura baffled, looking up at the arbiter for answers.

It turns out the King "sacrifice" was an illegal move.

What is an illegal move in chess?

As the name suggests, an illegal move is a move that goes against the rules of the game.

Imagine your opponent has given a check to your King. For some reason, you forget to defend against the check and play another move. Then the other move you've played will be an illegal.

1.a4 is an illegal move

1.a4 is an illegal move.

In this position, White's King is in check. If they forget to defend the check and play 1.a4, it will be an illegal move.

A move is considered officially illegal after a player has played their move and pressed the clock.

You can see illegal moves in many beginner games. But they sometimes occur even in top-level games, especially in faster time controls like the Blitz and Rapid.

Some famous players who've made illegal moves include heavyweights like Magnus Carlsen, Veselin Topalov, Vidit Gujrathi.

List of illegal moves in chess

This includes any move that breaks the rules of chess like:

  • Moving any piece on the board in a way that breaks the rule; for example - Moving a Rook diagonally, moving a Bishop vertically etc.
  • Ignoring a check and playing something else.
  • Castling when you're in check.
  • Castling even after you've moved the Rook where you want to castle.
  • Castling after you've already moved your King.
  • Pushing the pawn to the last rank and pressing the clock, without replacing the pawn with a piece of the same color.
  • Using 2 hands to make a move like castling, capturing, pawn promotion.
  • Pressing the clock without making a move.

What happens after an illegal move?

After an illegal move, an additional party gets involved in the game - the arbiter.

What should a player do?

The player whose opponent has made an illegal must claim the same to the arbiter.

What should an arbiter do? Penalty for making an illegal move.

If a player makes an illegal for the first time, the arbiter will give 2 minutes to their opponent in case of a rapid or classical game and 1 minute in case of blitz.

If a player makes an illegal move for the 2nd time, the arbiter can declare the game as lost for the defaulting player. This applies to blitz, classical or rapid format.

Illegal move in blitz chess

In a blitz, the first illegal move results in a time increase of 1 minute, while the second illegal results in a loss.

Imagine Alex and Tran are playing a blitz game. Alex makes the first illegal. As a penalty, the arbiter can give Tran 1 minute extra. If Alex defaults again, he will instantly lose the game.

How many illegal moves are allowed in chess?

Only 1 illegal move is allowed in chess, regardless of whether it is a classical, rapid or blitz game.

A 2nd illegal move results in an immediate loss.

The section for illegal move falls under the FIDE Handbook under Chapter E - Miscellaneous, Laws of Chess, Article 7: Irregularites.

Let's try to understand it in more detail in the coming section.

Irregularity in chess

Strange things happen in chess for which an arbiter must be prepared; irregularity is one of them.

Let's look at some irregularities below and discover how you should deal with them as an arbiter.

Starting the game with pieces on the wrong starting squares.

Imagine you're officiating at a chess event for beginners. The players start the game with pieces on the wrong colors like the one below:

Pieces placed on the wrong squares

Pieces placed on the wrong squares

The Bishop and Knights are out of place in the starting position. The players don't realize this until they play 5 moves. Not knowing what to do, they call you up and ask for your advice. What should you do now?

Under this case, The FIDE Handbook under Chapter E - Miscellaneous, Laws of Chess, Article 7.2.1 states the following:

"If during a game it is found that the initial position of the pieces was incorrect, the game shall be canceled and a new game shall be played."

So in the above case, a new game must be played.

Two players start the game with reversed colors

Imagine two players, Harry and Paul, get late to reach the venue. In haste, they check the pairings and sit at their respective boards.

They shake hands and quickly begin the game. They play the first few moves until they realize they've been playing on the wrong colors. Harry is playing White, when in reality, he should be playing Black.

Now they approach you. What would you do?

In this case, if less than 10 moves have been made, then the game shall be restarted. But if more than 10 moves are made, the game continues.

This can be understood under Article 7.3 which states:

"“If a game has started with colors reversed then, if less than 10 moves have been made by both players, it shall be discontinued and a new game played with the correct colors. After 10 moves or more, the game shall continue."

One player intentionally displaces their opponent's pieces

Harry and Paul are playing a blitz game. With limited time, Harry's hands start trembling and he unintentionally displaces pieces and presses the clock.

This means Paul has to adjust the falling pieces. Unhappy with that, Paul calls the arbiter and complains about it. What decision would you give you?

First of all, the player who displaces the pieces must adjust them in his own time. This should be made clear.

Then as an arbiter, based on your judgment, you can choose to punish the player who displaces the pieces. You can do this by adding time to the opponent's clock.


In almost every beginner tournament, you're likely to find someone who'll make an illegal move. Therefore, it's important to know what to do after such a move has been made. Hopefully, this blog gives you a good idea on what to do after players have made an illegal.

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