FEES AND EXPENSES - A PO or SOW will specify whether payment is based on time and materials or a fixed fee (as applicable, "Fees"). 1. Services and Deliverables.The SOW authorizes Agency to commence performing any Services as of the Effective Date. An SOW spells out the specific tasks, objectives, and responsibilities for a particular project. The MSA is a comprehensive, overarching contract, while the SOW is far more detailed.