What should I hold back from a buyer until they make a real offer?

No source used here lists the documents a seller must keep back from a buyer. One category does have a legal test attached: personal information about customers, employees and other individuals. For everything else, what you hold back is your decision, and the useful question at each stage is whether this buyer needs the item to decide anything yet.

The test for personal information

PIPEDA s.7.2(1) lets organizations that are parties to a prospective business transaction use and disclose personal information without the individual’s knowledge or consent if two conditions are met. They must have an agreement binding the recipient to use it solely for purposes related to the transaction, protect it with appropriate safeguards and, if the deal does not proceed, return or destroy it within a reasonable time. And the information must be necessary to decide whether to proceed and, if so, to complete the transaction. Section 7.2 is in addition to the circumstances in s.7(2) and (3).

Deciding is different from completing

The statute names two purposes: deciding whether to proceed with the transaction and, if the decision is to proceed, completing it. Ask yourself whether a summary would let the buyer decide, or whether the buyer truly needs individual names. If a record is needed only to complete, ask whether it can wait until the buyer has determined to proceed.

What happens after closing

If the transaction is completed, s.7.2(2) lets the parties keep using and disclosing the information that was disclosed under s.7.2(1) without consent if a further agreement is in place, the information is necessary for carrying on the business, and one of the parties notifies the individual within a reasonable time after completion. Ask your lawyer how that notice will be handled and by whom. Section 7.2(4) excludes a transaction whose primary purpose or result is the purchase or sale of personal information itself.

Everything else is your call

For non-personal material, write the stages down. Tell the buyer what is released at each one, and put it in a signed non-disclosure agreement before anything sensitive moves. The sequence in what to share with a buyer and when is one way to organize it, and your lawyer can adjust it to your business.