The general rule is that a contract is effective when both parties agree (ie, sign the Agreement of Sale) AND acceptance is communicated to the offering party. Construction contractors interested in performing construction contracts with the department must first complete the Vendor Registration process.The buyers provided a rather limited time for the sellers to consider their offer when they inserted a date in paragraph 5(a) of the agreement. Upon project completion, an itemized final invoice and completed NCP Form are required to be supplied to the municipality from the contractor. This is going to be how to fill out the agreement of sale for pennsylvania. The proposal includes the work to be completed and the price. Gov, select Treatment Services then Solicitation.