Again, the rights and obligations of the buyer and seller should be described in more detail in the contract or examined in depth when the goods are constructed in a complex, costly and customized manner according to a specific requirement. If the cost of the goods is paid over time and some refunds and fees must be paid. For example, milestone payments, advances, refunds, it is also advisable to verify and describe payment terms, payment times, payment requirements, taxes, interest, late fees, etc. under a separate title in the agreement. The document should indicate how benefits are accepted and how long the parties should review the work and provide feedback and make appropriate corrections. Objective work evaluation indicators that should be included in the service agreement can streamline this phase of the process. An agreement also creates responsibilities, conditions, manners, deadlines, monetary issues, etc., so that every angle of the agreement is properly sealed in the event of unforeseen losses.