A Committee conducting a competition on a net basis should review Section 9-2 of the USGA Handicap System when determining the Conditions of the Competition.
First and foremost, within Section 9-2 of the USGA Handicap System it recommends the Committee in charge of the Competition require the player to use the Handicap Index in effect on the date the competition commences. This is easy enough if the event is a one-day competition.
Further, the USGA also recommends, when practical, each player use the Index in effect at the time each round is played. This applies regardless of the length of the competition. Therefore, if a competition spans a revision date, a new Handicap Index resulting from the revision should be used in any rounds following the revision date. This could be a 54-hole member-guest at your club or even a season-long match-play competition which may extend for several weeks or months. The purpose is to have the player using the most current Index when each round is played. For example, your club may conduct a match play tournament which begins in May with the final match held in August. A player could be 15.1 in May and a 10.0 in August. The player should not be able to use the 15.1 when his current Index in August is substantially lower.
Another example is the member-guest competition consisting of five (5) nine-hole matches. If the competition begins on May 14 and the second-round matches are held on May 15, the player should use the Index in effect on May 15. In this situation, the Committee in charge of the Competition may elect to not change any Index for the final two days on Saturday and Sunday if this would create too much confusion and last-minute calculations. It is recommended that the Committee in charge of the Competition work with the Handicap Committee to make these decisions in advance of posting the competition calendar.
Remember under the National Revision Schedule, each Index must be revised on the 1st and the 15th of each month year round. A little advance planning in avoiding the revision dates will make sure the player is using the most recent Index for each round and will also minimize recalculating in the middle of the competition.