A signed document outlining a tenant's lease status is known as an
estoppel certificate. The tenant will certify certain lease facts in the tenant estoppel certificate, such as the security deposit amount and the rent payment, to involve a third party in their due diligence. The third party is typically a buyer or a lender. Black's Law Dictionary's explanation of an estoppel certificate may be difficult to understand if you're not an attorney. After this analysis, everything should be understandable.