Laws of Cricket 1980 Code - Law 12
1. Number of Innings
A match shall be of one or two innings of each side according to agreement reached before the start of play.
2. Alternate Innings
In a two innings match each side shall take their innings alternately except in the case provided for in Law 13 (The Follow-On).
3. The Toss
The captains shall toss for the choice of innings on the field of play not later than fifteen minutes before the time scheduled for the match to start, or before the time agreed upon for play to start.
4. Choice of Innings
The winner of the toss shall notify his decision to bat or to field to the opposing captain not later than ten minutes before the time scheduled for the match to start, or before the time agreed upon for play to start. The decision shall not thereafter be altered.
5. Continuation After One Innings of Each Side
Despite the terms of 1. above, in a one innings match, when a result has been reached on the first innings the captains may agree to the continuation of play if, in their opinion, there is a prospect of carrying the game to a further issue in the time left. See Law 21 (Result).
Notes
1. Limited Innings - One-Innings Match
In a one-innings match, each innings may, by agreement, be limited by a number of overs or by a period of time.
2. Limited Innings - Two-Innings Match
In a two-innings match, the first innings of each side may, by agreement, be limited to a number of overs or by a period of time.
Reproduction of the Laws of Cricket is by kind permission of Marylebone Cricket Club