The sale is not complete until the ownership transfer is official and money changes hands. Another way of putting it is that your sale is not done until you have been paid. It is not uncommon for a deal to go beautifully all the way to the closing where it suddenly falls apart. You need to keep the deal moving along all the way to the end if you want a successful sale.
Your business intermediary will ensure that all the paperwork is ready, all the necessary parties are notified, all the legal and regulatory requirements have been met, etc., before the closing. A qualified business intermediary will also walk all the parties through the closing to make sure all questions are answered and all necessary steps of the process are complete.