What happens when I call an illegal pitch?

An illegal pitch (improper pitching mechanics under rules 4.3.1 to 4.3.7) is a delayed dead ball, with these effects:

• Not hit: an extra ball is awarded to the batter (first base if it is ball four) and each runner advances one base. If a runner legally advances on the illegal pitch, passed ball or wild throw by the catcher, any extra bases obtained may be kept. A runner put out after advancing one base is out.
• Hit: the offensive team may take the award for the illegal pitch or the result of the play. If the batter reaches first base and all other runners advance at least one base, the illegal pitch is nullified, the play stands and no option is given.
• Interference first: if the batter-runner or a runner commits interference before advancing one base, the illegal pitch is nullified and the interference is enforced.
• Third strike situation: if the batter swings at and misses an illegal pitch that is a dropped third strike, and the catcher throws the batter out at first while other runners advance at least one base, the offensive team has the same option.
• If the team declines the play result: the ball is dead, a ball is awarded to the batter (first base if ball four) and all runners advance one base.
• Hits the batter: the ball is dead, the batter is awarded first base and all runners advance one base. No option is given.

Special effects apply to other pitching breaches: failing to release the pitch within 20 seconds is a ball awarded to the batter with the ball dead (rule 4.3.3 k), and a catcher who does not return the ball directly to the pitcher with no runners on gives the batter a ball (rule 4.3.6 b).