Combining two nine holes scores to form an 18 hole score
Combining two 9-hole scores - to make one 18-hole score - is easy...you do nothing other than enter 9-hole scores. Handicap System automatically takes the most recent pair of 9-hole scores to create an 18-hole score when there is an even number of 9-hole scores. If there is an odd number of 9-hole scores, Handicap System waits until another score is added to make a complete - and combinable - pair.
This figure shows sample 18-hole Adjusted Gross Scores (Adj Score) for "John Baker".
When we enter two 9-hole scores for John Baker as shown in the next image...
...the above two 9-hole Adjusted Gross Scores (Adj Score) - 43 and 46 - are added together to form one 18-hole score - an 89C (see top Adj Score circled in next image below). Items of note about combined scores:
Finding the Combined 18-hole Score
Finding the 18-hole score resulting from the combining of two 9-hole scores is easy. Look for the more recent date of the two 9-hole scores and then find that date in the 18-hole score list. The score with that date and a "C" - for Combined - next to the Adjusted Score is the 18-hole score that corresponds to the two 9-hole scores used. For example, if you look at the list of two 9-hole scores above, the more recent date is 3/13/2014. When we look for a score dated 3/13/2014 with a "C" next to the score in the 18-hole score list immediately above this paragraph, we find it is the score at the very top of the list.
Editing Combined Scores
Editing a combined 18-hole score does not change the two 9-hole scores used. Nor does editing one or both of the 9-hole scores used change the already combined 18-hole score. If you need to make a change, the same change must be made to both the 9-hole score(s) and the resulting 18-hole score.
USGA on 9-hole Scores
Note: From Section 5-2 of USGA Handicap System:
c. Posting Nine-Hole Scores
To be acceptable for handicap purposes, nine-hole scores must meet the following conditions:
(i) The course must have a nine-hole USGA Course Rating and Slope Rating;
(ii) At least seven holes must be played.
There is no restriction on the number of nine-hole scores posted to a player's scoring record. Even if a player plays a majority of nine-hole rounds, that player can still utilize a Handicap Index (See Section 10-2) rather than a Handicap Index (N). (See Section 10-5 for computation of a Handicap Index (N).) (See Decision 5-2c/1.)
d. Treatment of Nine-Hole Scores
Once posted, a nine-hole score will be treated as follows:
(i) Nine-hole scores must not be designated as T-Scores;
(ii) When two nine-hole scores are combined, the USGA Course Rating is the sum of each nine-hole USGA Course Rating and the Slope Rating is the average of the Slope Rating of the two nines (if the average is .5, it is rounded upward to the next whole number);
(iii) Two nine-hole scores combined to create an 18-hole score should be designated with the letter C (e.g., 85C). If either of the two nine-hole scores was posted via Internet (See Section 5-2a(vi)), the score should be designated CI;
(iv) Nine-hole scores are combined in the order that they are received into the player's scoring record from any club or from any combination of nines, regardless of score type. For example, a front nine middle tee score could combine with a front nine back tee score made from any course.
An 18-hole score created by the combination of two nine-hole scores will display the date and course name (if applicable) of the latest nine hole score (e.g., April 29 and May 4 = May 4).
A nine-hole score will be retained for combination with another nine-hole score until it is older than the twentieth oldest eighteen-hole score in the scoring record, and nine-hole scores will be combined in the order they are received in the player's record, and "not necessarily by date."