If the organisers of a Go tournament in Britain, recognised by the BGA, do not specify otherwise, then the AGA-style rules apply.
If overtime is to be used, then unless stated otherwise, Canadian overtime applies.
A printable form of the default rules can be downloaded for publication bga_tour_rules.pdf.
The rules given in this page and in the documents cited above are only default rules. A tournament director may instead use whatever rules she chooses, as long as they are clearly specified in all material about the tournament.
Black gives White 7½ points komi.
Triple kos and other such repeated positions are prevented by a "Superko" rule. You may not play a stone to create a board position that you created on a previous play..
Japanese professional games traditionally use the byoyomi system. When a player has only a few minutes left the seconds are counted down, and any move made in less that a minute does not use up any of that player's time.
In Britain we use Canadian Oovertime system instead. When a player has used all of their main time allocation, they go into overtime. Overtime is made up of an unlimited number of overtime periods. When a player has used the main allocation, the first overtime period begins.
In each overtime period the player must play a specified number of moves within a specified time period. Typically, the main allocation might be one hour each, and the overtime periods for each might be five minutes in which to play thirty stones.
A move consists in placing a stone on an intersection (and removing any consequent captures), or passing, and then pressing the clock. A player who fails to make the specified number of moves within the specified time period loses immediately.
If a player plays the specified number of stones within the specified interval, then next overtime period begins immediately. The player's opponent re-sets the clock for the next overtime period, and while this is being done the player counts out the required number of overtime stones. The next overtime period begins when the player's opponent next presses the clock.
Tournament organisers are free to specify any method of timekeeping that they choose, including traditional byoyomi (if you can find lots of willing time-keepers), or no overtime at all, i.e. sudden death. However if a sufficiently eccentric method is used then the tournament may not be eligible for inclusion in the European ratings system; and in any case you must clearly state any overtime variations in your tournament publicity.
Often, each overtime period will be identical, with the same number of stones to be played in the same interval. For example twenty stones in five minutes (commonly abbreviated 20/5) or thirty stones in five minutes (30/5).
If your tournament hall is available for a tightly controlled time and you cannot afford to overrun your schedule, you may consider opting for accelerated overtime in which each overtime period is again the same, but the number of stones increases in each period. So for example 20/5, then 30/5, then 40/5, then 50/5 and so on. This guarantees a known maximum time for each game!
Some tournament organisers choose to specify a sequence of differing periods (the same sequence for both players). For example 20/10, then 20/5, then 40/5, then 40/5.
A player loses by default if late by half the main time allocation. A player arriving more than 20 minutes late must inform the referee when he does arrive.
| Chapter 11 | Organisers' Handbook | Appendix B |
| Pt. II: Running a Tournament |