An Illinois subcontractor agreement allows a contractor to hire a subcontractor to help complete a particular job. The contract will outline the duties, responsibilities, and liabilities of the subcontractor, and will protect the client by ensuring the contractors are held liable if they don’t complete their work. Contractors will hire subcontractors when a project requires additional labor or specialized skills. For instance, trained plumbers, carpenters, drywallers, stonemasons, and electricians may need to be hired as subcontractors to complete the construction of a home.