How much history do you need to support a VSOE determination?

Determination of what is sufficient sales history in order for a company to establish VSOE is a matter of facts and circumstances. I suggest using a "bell-curve" approach supporting a normal distribution with at least 80% to 85% of sales prices within a range of plus or minus 15% of the median price. The narrower the range of prices within the median range, the quicker the company may establish VSOE of fair value. I suggest that you consult with an experienced revenue accountant as well as your audit firm.