TBL refers to triple bottom line. The triple bottom line is a form of reporting that takes into account the impact a business has in terms of social and environmental values along with financial returns. It is also known as three pillars; people, planet and profit. It is the financial, social, and environmental effects of a firm's policies and actions that determine its viability as a sustainable organization.
Triple bottom line accounting recognizes that without happy, healthy people to staff a business and the natural environment able to sustain those people and supply resources for trade; business is, well, simply unsustainable in the long run. Triple bottom line reporting is becoming an accepted way for businesses to demonstrate that they have strategies for sustainable growth.