When does a tie-break occur in a game of tennis?

Answer 1

At 6 all in a set, then you play a 7-point-tie break. Sometimes, you play a 10-point-tie break in the lieu of the third set... it depends.

To improve on this answer I have played tennis for years so in a set you play a tie breaker in a 5 all set

Answer 2

A Tie break occurs at 6-6.

There is no tie break in the final set of the grand slam events.