When food or chemical companies are calculating what the hottest pepper is, we work with the most consistently highest average heat. This gives us a determination of heat level that is consistent across the board. Chilli peppers can range in heat by a ration of 10 to 1. It is not uncommon for the lowest heat score of a pepper to be 10 times less than the same pepper's highest heat score.
That said, the current highest individual pepper's recorded heat is the Trinidad Moruga Scorpion grown by the Chile Pepper Institute of New Mexico. BUT, it does not consistently score a high enough average to be given the record nor title of "hottest chilli pepper". Many peppers have higher average heat levels.
The current hottest chilli pepper of record is the Carolina Reaper grown by Ed Currie of Puckerbutt Pepper Company in the US. They were granted the record in November 2013.
If you want to know who actually holds the pepper record at any given time, Guinness World Records tends to be the place to go to earn the title, why? Because their title goes to the pepper that scores the highest average. They and the pepper industry established this basis as a result of the efforts of ASTA, the American Spice Traders' Association with the work of the Chile Pepper Institute of New Mexico.