Sales forecasting is essential for Supply Chain stock optimization and inventory flows management. Although a simple concept, sales forecasting is misunderstood by many. To fully comprehend the attributes of sales forecasting, it is vital to understand the nature of a forecast, how it is used, created and interpreted. Intuition alone is inadequate when referencing mathematical models, impact factors or probability. Here, we examine five popular beliefs about sales forecasts in the Supply Chain. We clarify the fundamental concepts with examples to help readers use the sales forecasts wisely and with unbeatable results.