The schedule of values document itemizes the costs for tasks, personnel and supplies the contractor needs to complete the project. It consists of trade categories (e.g., plumbing, painting, welding, and more) and the estimated labor (including subcontractors), materials and contingency amounts. The sum of the costs in this document is the guaranteed maximum price. While using the schedule of values is generally to reduce uncertainty, it can be a source of confusion and disagreement when the contractor's numbers are out of line with the customer's expectations.