The short answer: There is none.
For handicap purposes, the USGA imposes stroke limits (called Equitable Stroke Control, or ESC) to prevent golfers from sandbagging one hole to keep their handicaps high. Thus, when you enter a score into MyScorecard, we ask you to adjust that score for any holes where your strokes exceed that limit.
However, when you’re on the course, there is no “maximum” to take. Even a professional golfer can run up scores into the double digits. And just to prove a point, back in April of this year, Tour Player Kevin Na posted a 16 on the par 4 ninth hole at the Valero Texas Open.