An estoppel certificate is a written statement setting forth facts about a piece of real estate such as the unpaid principal balance of a mortgage and the interest rate. Its purpose is to stop a future claim that the amount owed is different from the actual unpaid balance, or that the interest rate is other than the contracted rate.

In real estate a purchaser of the premises from the landlord will request estoppel certificates from the tenants. The estoppel certificate normally refers to an annexed true copy of the lease and should include a conformation that (1) the lease is in full force and effect;(2) the lease has not been supplemented, amended, or modified in any respect; (3) no default under the lease exists and no event has occurred that, with the giving of notice and/or lapse of time, would become a default under the lease; and (4) there are no defenses, setoffs, recoupments, claims, or counterclaims of any nature by or on behalf of such party against the other.