Activity-Based Costing

An ABC system is designed to match overhead costs as closely as possible with company activities. By doing so, overhead costs can be reasonably associated with products, departments, customers, or other users of activities, which tells managers where overhead costs are being used within a company. This results in much better control over overhead costs.

There are several ways to allocate overhead costs. Some overhead costs, such as utilities, are associated with specific machines. For example, a machine may require ten cents of electricity per minute. If so, this overhead cost can be charged out to those products that are run through the machine, based on the time spent being worked upon it. Other overhead costs are associated with a specific product line, and can reasonably be allocated to the activities performed within that product line. For example, there is typically a supervisor who is assigned to a single product line. If so, the fully burdened salary of this person can be charged to such related activities as production and maintenance scheduling. Still other overhead costs may be grouped by commodity used in the production process. For example, each member of the purchasing staff may be responsible for the procurement of a specific commodity. If so, this overhead cost can be distributed to individual products based on their usage of the commodity. Clearly, there are many valid ways to allocate overhead costs to various activities, and from there to users of those costs. An ABC system creates a structured approach to the accumulation, storage, and allocation of overhead costs using many of these activity measures.

An ABC system is a difficult and complex one to create, because of the wide variety of costs that must be accumulated, tracked in relation to different types of activities, and charged off. Here are the primary steps involved in creating such a system:

Determine the scope of the system. A fully developed ABC system that encompasses all costs throughout a company is a massive undertaking that may not yield any results for several years. A better approach is to conduct a gradual rollout of the system that produces results more quickly. Accordingly, a key factor is limiting each incremental rollout of the system to a carefully defined segment of the business. The determination of scope should also include a review of the level of detailed analysis that the system is to produce, since an excessive focus on detail may result in a system that is too expensive in relation to the utility of the information produced.
Set aside direct costs. There will be several direct costs that can be clearly and indisputably traced to specific products. These costs should be identified early in the design phase, so that they will not be erroneously added to the ABC allocation system.
Locate costs in the general ledger. The next step is to identify each of the overhead costs in the general ledger that will be allocated by the ABC system. This can be a difficult undertaking, for the required costs may be lumped together in the ledger, and must be segregated through a new data collection system that involves the creation of a new general ledger account number. Alternatively, the split may be achieved less accurately by allocating a percentage of the cost in a single general ledger account to several overhead cost items which will then be allocated.
Store costs in cost pools. All of the costs that have been identified within the general ledger must now be stored in a series of cost pools. Each cost pool accumulates costs that are similar to each other. For example, a building cost pool will include the costs of insurance and maintenance for a building, whereas a product line cost pool may include the marketing and supervisory costs that can be traced to a specific product line. A third type of cost pool is one that is related to a specific production batch, and can include such costs as production control labor, tooling, materials handling, and quality control. The total number of cost pools used will have a direct impact on the maintenance costs of an ABC system, so the design team must balance the increased allocation accuracy associated with more cost pools with the extra labor needed to maintain them.
Determine activity drivers. Having summarized overhead costs into a set of cost pools, we must now allocate them, which we do with an activity driver – this is a variable that reasonably explains the consumption of costs from a cost pool. For example, some accounts payable costs are closely associated with the number of checks printed and mailed, while some engineering costs vary directly with the number of design changes added to a product. Examples of other activity drivers are the number of machine setups, the number of maintenance work orders, the number of purchase orders, and the number of customer orders processed. Whichever activity driver is chosen as the basis for cost pool allocation should be easy to calculate, require minimal data collection, and have a reasonably close cause-and-effect relationship with a cost pool.
Spread costs from secondary to primary cost pools. Some of the cost pools include costs that are, in turn, distributed to other cost pools. These costs are usually for internal company services, such as management information systems services that are provided to other departments. These secondary cost pools must be allocated to primary cost pools.
Calculate the overhead cost per activity unit. We then divide the total number of occurrences of each activity driver into the total amount of costs in the primary cost pools for the accounting period, which results in a dollar figure per unit of activity.
Assign activity costs to cost objects. The final step is to calculate the usage of each activity driver by a cost object (which is anything that uses activities, such as products or customers). For example, if a product requires the creation of two purchase orders (which are activity drivers) and the ABC system has determined that each purchase order requires $32.15 to create, then the amount of overhead charged to the product will be $64.30.

In brief, the ABC process involves taking costs out of the general ledger and assigning them to either secondary or primary cost pools, which are then distributed to cost objects through the use of activity drivers.