An activity-based costing system that is designed for internal decision-making will not conform to generally accepted accounting principles (GAAP) because: Multiple Choice Some manufacturing costs will not be assigned to products. Some non-manufacturing costs would not be assigned to products. First-stage allocations may be based on subjective interview data. All of the above are reasons why an activity-based costing system will not conform to GAAP. None of the above because activity-based costing does conform to GAAP.