An estoppel certificate is a signed tenant statement confirming lease terms, rent, and that no defaults exist, relied on by buyers and lenders.
Buyers and lenders typically rely on estoppels, so the buyer will normally request one from the tenant during due diligence. It confirms the lease documents, the rent, the term, any options, the security deposit, and that neither side is in default. If the tenant's answers differ from the seller's, that is a signal to dig deeper before closing. The purchase agreement should state the form of estoppel required and what happens if the tenant does not provide it.