Sell agreement is a contract made between shareholders that limits a shareholder's actions in the sale or transfer of shares if they leave the company. Appendix A: Site References; Legal Description.A Stock Purchase Agreement (SPA) is a formal contract that enables businesses to document the buying and selling of company stock between a seller and a buyer. Our Utah-based attorneys can assist your company with a variety of business transaction, contracts and ancillary agreements. Parr Browns contract attorneys are some of the best in Utah. Offering guidance in contract development, corporate structure, organization, and much more!