An activity-based costing system that is designed for internal decision-making will not conform to generally accepted accounting principles because: under activity-based costing the sum of all product costs does not equal the total costs of the company. under activity-based costing manufacturing costs are assigned to products. activity-based costing has not been approved by the United Nation's International Accounting Board. activity-based costing results in less accurate costs than more traditional costing methods based on direct labor-hours or machine-hours.