An activity-based costing system that is designed for internal decision-making will not conform to generally accepted accounting principles because: multiple choice 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. under activity-based costing the sum of all product costs does not equal the total costs of the company. under activity-based costing some manufacturing costs (i. e., the costs of idle capacity and organization-sustaining costs) will not be assigned to products.