Change orders can be initiated by the client (adding, removing, or modifying scope after contract execution), the contractor (field conditions discovered during construction, or drawing ambiguities requiring field resolution through the RFI process), or the building department (code requirements not addressed in the original design). Regardless of who initiates the change, the process is the same: scope is documented, cost and schedule impact are calculated, the change order is presented to the client, and work proceeds only after both parties sign. The reason for the change is documented because it determines cost responsibility — client-initiated changes are paid by the client; estimating errors or omissions are the contractor’s cost; unforeseeable field conditions are typically the client’s cost; design errors may be the designer’s professional liability.