Job estimates and invoices are provided in a written format. All primary estimates are subject to review prior to the project start date. When a final written estimate is provided, an acceptance signature will be supplied at the bottom of the form. If the project terms or objectives change after the project start date, then a new estimate will be submitted for approval within 48 hours. All changes will be spelled out on the new project estimate, and the number of estimate changes will be tracked and recorded to ensure that both parties maintain current and up to date information for the project. An open project estimate is not valid unless it is signed by the customer, and the most recent signed estimate will be the document that is in force and utilized for final billing and invoicing. If the customer requires additional copies of written estimates, the copies will be provided upon request. The contractor will maintain all original signed estimates, and will make copies available to the customer.