The World Handicap System (WHS) came into being on January 1, 2020. One of the items that changed with the WHS is how the Adjusted Gross Score is determend. In the Rules of Handicapping for the USGA, Rule 3, Adjustment for Hole Scores states:
A score for handicap purposes should not be overly influenced by one or two bad hole scores that are not reflective of a player’s demonstrated ability. In addition, incomplete scores and/or scores where a player did not hole out on every hole can provide reasonable evidence of the player’s ability and can be used for handicap purposes. Rule 3 covers the circumstances where scores may be acceptable and how these hole scores should be adjusted.
The main method of arriving at the Adjusted Gross Score is to adjust each hole downward to net double bogey, if necessary. That means, for handicapping purposes, a player can have up to Par + 2 (strokes) + any handicap strokes received on that hole. For example, if par is 5 and a player receives 1 stroke on the hole, for handicapping purposes, the hole score is limited to 5 + 2 (strokes) + 1 (handicap strokes received on hole), or 8. Each hole where a player shoots higher than net double bogey must be adjusted downward to net double bogey. The number of strokes a golfer receives is determined using their full, unrestricted Course Handicap. The Course Handicap is rounded to the nearest whole number.
There are two exceptions: when a player doesn't yet have and Index and when a player's Course Handicap is more than 54. If a golfer does not yet have an Index, each hole is adjusted to par + 5 strokes, if something higher is shot. That means, if someone shoots a 9 on a par three hole, for handicapping purposes the score is adjusted down to 8 (3 + 5). If a player has an Index, but their Course Handicap is above 54, for handicapping purposes, each hole is adjusted down to par + 5, if they shoot a higher score than that.
The example below shows a scorecard for George. On hole 9, a par 5, he shot a 9. For handicapping purposes, the maximum allowed is an 8 (Par + 2 + handicap stroke of 1 = 8). For handicapping purposes, his hole 9 score is reduced to 8 and his total Adjusted Gross score is reduced from 87 to 86.
The "Adjusted Gross Score" is one of the ways that the USGA uses to make sure a player's handicap represents his or her potential. Rather than use an unusually high score on a hole to include in a portion of the handicap calculation, for handicapping purposes, that high score is adjusted downwards according to the player's Course Handicap. The USGA Handicap Manuals says...
An "adjusted gross score" is a player's gross score adjusted under USGA Handicap System procedures for unfinished holes, conceded strokes, holes not played or not played under the Rules of Golf, or Equitable Stroke Control.
Reformatting for clarity, the above statement would look like this:
An "adjusted gross score" is a player's gross score adjusted under USGA Handicap System procedures for...
Much of the time what we're really concerned with is the adjustment to scores using Equitable Stroke Control. Equitable Stroke Control specifies that, for handicapping purposes, a player has a maximum number s/he can put down for any hole depending on his/her Course Handicap for the course/tee combination s/he happens to be playing.
The scorecard below shows both gross score and adjusted gross score for each hole. In this example, the scorecard is for a player with a Course Handicap of 4 on the course/tee he is playing. Equitable Stroke Control requires that he post a maximum of double bogey on any given hole, if his Course Handicap is 9 or less for 18 holes. On holes 11, 12 and 13, his gross scores were more than a double bogey, so - for handicapping purposes - his adjusted gross score is adjusted downward to 5, 7 and 6 respectively, or double bogeys. For competition purposes, each of those same three holes is counted as a triple bogey...ugh!
For each course/tee combination you will have a calculated Course Handicap. Knowing your Course Handicap, you can look up the Equitable Stroke Control table and determine the highest adjusted gross score you are allow