The Terms of the Competition set out the structure of the competition and once a competition has started, the terms will only be altered in very exceptional circumstances.
Since players begin a round with the expectation that a certain number of holes will be played and may base their play on that, the number of holes to be played in a round should not be changed once that round has started. For example, if bad weather results in play being suspended after all the players have completed 9 holes of an 18 hole round, the Committee should not announce the results based on only 9 holes.
If circumstances such as bad weather affect the number of rounds that can be played in the time available, the number of rounds to be played, or number of holes in any rounds not yet started, may be altered to accommodate the circumstances. Similarly, if those circumstances mean the planned format cannot be accommodated in the time available, the format of the competition may be changed.