The document discusses unit based costing (UBC) implemented at Hindustan Petroleum Corporation Ltd. UBC accumulates overhead costs for different organizational units and then assigns costs to products/services based on their use of activities in each unit. The key units considered are Fuel Refinery, Lube Refinery, and Captive Power Plant. UBC aims to provide more accurate product cost estimates for management decision making compared to traditional cost accounting. It involves identifying overhead costs like utilities, employee costs, maintenance etc. and allocating them to units based on cost drivers.