The first step is to have the contractor complete Form W9, Request for Taxpayer Identification Number and Certification. How do I fill this out?The following Supplementary Conditions modify the General Conditions. (A201 -- 2007) of the Contract for Construction. Check only one: Joint agreement to affirm independent relationship for certain building and construction workers. Acts as a liaison between Tarrant County and other governmental entities utilizing Cooperative Programs. Contractors: Construction workers, plumbers, electricians, and other tradespeople who are hired to complete specific projects or tasks. This agreement is effective upon the date of approval in Tarrant County Commissioners Court.