If there is consensus on the sale of the shares in a company, a contract is drawn up to make it official. That contract is a Share Purchase Agreement (SPA). It determines what is bought (which shares) and the price (including earn-out constructions etc.) is also determined. The SPA also contains a large number of provisions relating to breaches of warranties. Each SPA is custom-made because indemnities and many other particularities must be regulated in it.
Practice shows that the SPA is not drawn up and negotiated within a few days. It is a voluminous contract on which much depends. Moreover, it is not only the client who will have an influence on the content, from a tax point of view it also needs to be carefully reviewed.
Once the SPA is complete, the shares can be delivered by notarial deed. This is often the capstone of a long signing session.