Rule of 90
 
The rule of 90 applies to a player who’s meets the following criteria: 

• Their age plus index totals 90 or more. 
• Has an index that normally qualifies them to compete in the C flight and therefore play from the blended tees

 
In flighted competitions, these players play fin the D-flight (rust tees).
In non-flighted competitions, these players play from the rust tees.
 
Example: 

• Player Y is 73 years old and has an index of 17.3.  His age plus index is 90.3
• Normally he would be a C-flight player, playing from the pine-rust tees with a course handicap of 14
• Under rule 90, he plays in the D-flight from the rust tees with a course handicap of 11.

 
Notes: 

1. If a player elects to play under either of these two rules, he must continue to play under this rule for at least one year.                                                                                    
2. Because of a change in the way course handicaps are calculated under the 2020 Global Handicap System, there is no requirement to make a manual change the player’s handicap index.