What do I do about a thrown ball or a deliberate front-foot no ball?

Under the MCC Laws of Cricket (2017 Code, 4th Edition 2026):

Thrown or underarm delivery (Law 21.2 and 21.3)

• A delivery is fair in respect of the arm if, once the bowler's arm has reached shoulder level in the delivery swing, the elbow joint is not straightened partially or completely until the ball has left the hand. Flexing or rotating the wrist is allowed.
• The striker's end umpire has primary responsibility for judging this, but the bowler's end umpire may also call No ball if they consider the ball was thrown.
• Underarm bowling is not permitted except by special agreement before the match.
• First offence: call and signal No ball. When the ball is dead, the bowler's end umpire warns the bowler (a first and final warning that applies throughout the innings), tells the fielding captain the reason, and informs the batters.
• Further offence by that bowler in the innings: call and signal No ball, then direct the fielding captain to suspend the bowler immediately. Another bowler completes the over (not one who bowled the previous over or may bowl the next). The suspended bowler cannot bowl again in that innings.
• The umpires together report the occurrence after the match to the offending side's Executive and any Governing Body responsible for the match.

Deliberate front-foot No ball (Law 41.8)

• If you consider the bowler delivered a deliberate front-foot No ball, immediately call and signal No ball. When the ball is dead, direct the fielding captain to suspend the bowler immediately and inform the other umpire.
• The suspended bowler cannot bowl again in the match. Another bowler completes the over, and the umpires report the occurrence after the match.