The costs that may be considered in applying the cost plus method are limited to those of the supplier of goods or services. This limitation may raise a problem of how to allocate some costs between suppliers and purchasers. There is a possibility that some costs will be borne by the purchaser in order to diminish the supplier’s cost base on which the mark up will be calculated. In practice, this may be achieved by not allocating to the supplier an appropriate share of overheads and other costs borne by the purchaser (often the parent company) for the benefit of the supplier (often a subsidiary). The allocation should be undertaken based on an analysis of functions performed (taking into account assets used and risks assumed) by the respective parties as provided in Chapter I. A related problem is how overhead costs should be apportioned, whether by reference to turnover, number or cost of employees, or some other criterion. The issue of cost allocation is also discussed in Chapter VIII on cost contribution arrangements.