A signed statement certifying that certain statements of fact are correct as of the date of the statement and can be relied upon by a third party, including a prospective lender or purchaser. In the context of a lease, a statement by a tenant identifying that the lease is in effect and certifying that no rent has been prepaid and that there are no known outstanding defaults by the landlord (except those specified).

The definition of an Estoppel is a bar or preclusion. This preclusion preludes a person from denying the factual truth about the leased premises.  It is an equitable doctrine and is used when good conscience requires it. An Estoppel Certificate is distinguished from a waiver in that a waiver generally refers to a voluntary surrender or relinguishment of some known right or benefit; an estoppel creates an inability to assert it.