In this paper, we focus on the returns generated by assets that are not reported. These refer mainly to the assets other than those reported on the balance sheet. These sources create value to organisations. Traditional capital e.g. physical and human capitals cannot guarantee future success of a business. We define and include social capital as an internal-based source and market capital as an external-based source for sustainable business performance. These intangible assets may represent a huge source but at the same time they are the hardest to quantify and express numerically and tangibly. There is a lack of a standard metric method to measure this kind of knowledge and assests. Ontology, a particular type of knowledge based technology, can be used to help understand how knowledge within organisations creates value. By making knowledge explicit and transparent, it promotes trust which in turn promotes governance. Generally speaking, an ontology is used to explicitly express how the intellectual capital is valued and thus results are sensible for managers. The ontology enables evidence based formation of knowledge valuation.