17.1 Number of balls
The ball shall be bowled from each end alternately in overs of 6 balls.
17.2 Start of an over
An over has started when the bowler starts his/her run-up or, if there is no run-up, starts his/her action for the first delivery of that over.
17.3 Validity of balls
17.3.1 A ball shall not count as one of the 6 balls of the over unless it is delivered, even though, as in Law 41.16 (Non-striker leaving his/her ground early) a batter may be dismissed or some other incident occurs without the ball having been delivered.
17.3.2 A ball delivered by the bowler shall not count as one of the 6 balls of the over
18.104.22.168 if it is called dead, or is to be considered dead, before the striker has had an opportunity to play it. See Law 20.6 (Dead ball; ball counting as one of over).
22.214.171.124 if it is called dead in the circumstances of Law 126.96.36.199. Note also the special provisions of Law 188.8.131.52 (Umpire calling and signalling Dead ball).
184.108.40.206 if it is a No ball. See Law 21 (No ball).
220.127.116.11 if it is a Wide. See Law 22 (Wide ball).
18.104.22.168 when any of Laws 24.4 (Player returning without permission), 28.2 (Fielding the ball), 41.4 (Deliberate attempt to distract striker), or 41.5 (Deliberate distraction, deception or obstruction of a batter) is applied.
17.3.3 Any deliveries other than those listed in 17.3.1 and 17.3.2 shall be known as valid balls. Only valid balls shall count towards the 6 balls of the over.
17.4 Call of Over
When 6 valid balls have been bowled and when the ball becomes dead, the umpire shall call Over before leaving the wicket. See also Law 20.3 (Call of Over or Time).
17.5 Umpire miscounting
17.5.1 If the umpire miscounts the number of valid balls, the over as counted by the umpire shall stand.
17.5.2 If, having miscounted, the umpire allows an over to continue after 6 valid balls have been bowled, he/she may subsequently call Over when the ball becomes dead after any delivery, even if that delivery is not a valid ball.
17.6 Bowler changing ends
A bowler shall be allowed to change ends as often as desired, provided he/she does not bowl two overs consecutively, nor bowl parts of each of two consecutive overs, in the same innings.
17.7 Finishing an over
17.7.1 Other than at the end of an innings, a bowler shall finish an over in progress unless incapacitated or suspended under any of the Laws.
17.7.2 If for any reason, other than the end of an innings, an over is left uncompleted at the start of an interval or interruption, it shall be completed on resumption of play.
17.8 Bowler incapacitated or suspended during an over
If for any reason a bowler is incapacitated while running up to deliver the first ball of an over, or is incapacitated or suspended during an over, the umpire shall call and signal Dead ball. Another bowler shall complete the over from the same end, provided that he/she does not bowl two overs consecutively, nor bowl parts of each of two consecutive overs, in that innings.
© Marylebone Cricket Club 2017