An estoppel certificate is a document that is used to keep individuals from asserting different facts from those already agreed upon in the text. Estoppel certificates are common in landlord-tenant disputes. Estoppel is generally a rule of evidence that keeps a person from denying a truth that has already been agreed upon. The word is derived from an old French word that means stopper plug. As an example, you are renting a great home from your landlord, but heavy construction seriously interferes with your enjoyment of the premises. The unit above you is undergoing a restoration, and your home is filled with dust, noise and constant irritation. You consult the landlord and are given a huge rent reduction. You are given an estoppel certificate that gives you a number of rights and states the new rental price. In the future, you can use the certificate to estoppel the landlord from collecting the full rent. You have an estoppel certificate that states the new rent amount, and the landlord cannot dispute the facts.