A change order is a formal document that modifies a construction contract by adding, deleting, or revising work from the original scope. Change orders arise when unforeseen conditions are discovered (like unexpected soil problems), when the owner requests modifications, when design errors must be corrected, or when regulations change during construction. Each change order specifies the altered work, cost impact, and schedule adjustments, requiring approval from both parties. Change orders can significantly affect project budgets and timelines. Municipal projects track change orders carefully to maintain accountability and explain why final costs may differ from original contract amounts.