In real estate an Estoppel Letter is a letter from the management company stating that there are no outstanding debts owed to the homeowner's association by the seller such as maintenance fees, outstanding taxes, special assessments, when the next maintenance fees are due and availability.

In mortgages an estoppel letter is a document executed by a party to a debt acknowledging the current loan balance and terms. Having thus acknowledged the balance and terms, the party making the document is prevented from later claiming that the information was not accurate. It is used to confirm the loan balance in connection with the sale of a mortgage by the mortgagee or in connection with the sale of the underlying real property by the mortgagor.