A change order is a written amendment to an existing contract after the effective date that alters the work, the contract sum, or the contract time. In project management, change orders are also called variations or variation orders. Any modification or change to works agreed in the contract is treated as a variation. Change orders are common in most projects, and they are very common in large projects. They are used to modify the original scope of work of a contract, and depending on the magnitude of the change, it may or may not alter the original contract amount and/or completion date. Change orders can be caused by various factors, including errors and omissions in plans and drawings, unforeseen site conditions, owners desire to change the original plans, and changes in laws and regulations. A change order may force a new project to handle significant changes to the current project. Once a change order is submitted and approved, it generally serves to alter the original contract such that the change order now becomes part of the contract.