Here, we review recent empirical advances that have improved our understanding of why and when sex change occurs. We show that sex-changing animals use a greater diversity of strategies to increase their reproductive success than was previously recognized: some individuals change sex early, others change sex late, some individuals change sex more than once, and others do not change sex at all. These different strategies can be unified by the principle that individuals change sex when it increases their reproductive value. The breeding tactics (male, female or non-breeder) adopted by individuals often appear to be adaptive responses to their own social-ecological context and variation in these conditions results in significant differences in the timing of sex change within and between species.