The notion of basis is crucially important in determining the tax consequences that result from virtually any property-based transactions, whether it is the sale of $100 of stock, or a $10,000,000,000 merger of two multinational corporations. It's important, then, to answer one key question: What exactly is basis? How is it used in calculating the gain or loss that results from the sale of capital property? What is the rationale or justification for considering basis in calculating the amount of gain or loss?