The quick line change rule is typically called on an attacking player in one of two situations:

• While dribbling with the ball, the attacking player quickly turns the ball or changes the right of way into a defending player, causing a collision or bump without allowing them the time to clear the new line. 
  
  
• While established on the line of the ball and approaching, a player can turn their mount into a defending player creating illegal contact on a new line when they should have continued forward. 

The penalty for breaking this rule comes in two parts. If it is a foul by the attacking player, riding into the defending player, it will be a penalty against the attacking player. If the defending player does not leave the line of the ball quickly enough, it will be a foul against the defending player.

The outcome and ball placement are determined on who the umpire thinks has made the offense. If the defending player does not clear the line of the ball quickly enough, it will be a foul against him and a penalty awarded against him. If the attacking player does not allow the defending player to clear and either rides into him or hits into him with his stick or the ball, a foul will be called against him. A penalty should always be called against a player, hitting into a horse and potentially a yellow card could be awarded.

The outcome and ball placement are determined by who the umpire determines has made the foul. If the defending player does not clear sufficiently quickly, a penalty should be awarded against him. If however, the attacking player does not allow sufficient time for the defending player to clear the line. A foul should be awarded against him. If the attacking player rides into the back of the defending player or hits the ball or his stick into the defending player's horse, a greater penalty should be awarded.

The game should always be started with a penalty against the player who has fouled. However, in certain circumstances both the defending player and the attacking player might well have fouled, the defending player by not clearing sufficiently quickly and the attacking player by not allowing him (defending player) to clear the new line sufficiently. In this case offsetting fouls may be called and a throw in awarded.

There is a slight difference in the quick line change between high goal polo and low goal polo. The skill of the player in changing the line of the ball quickly and somewhat better horses in high goal polo allow players to enter or indeed leave the play quickly and safely. Thus, there is a slight difference, but mainly in the pace of the horse and the skills of the players involved.

The most common error by a player who has made a quick line change is not allowing the defending player who was already in the position, sufficient time to leave the new line of the ball and riding into the back of him or hitting into him with the ball or stick. This is the most common and happens frequently.