It is not his or her deed. A defence raised where a person has completed a deed in ignorance of its character. notary public A person, usually a solicitor, who prepares, authenticates and witnesses international documents, in particular for use in non-Commonwealth countries. They perform similar functions to a Justice of the Peace but are recognised by foreign courts and authorities and can charge for their services.

A basis of a claim which can be made to deny a contract by one seeking to avoid its conditions.

Latin for "not his deed" and a special defense in contract law to allow a person to avoid having to respect a contract that she or he signed because of certain reasons such as a mistake as to the kind of contract. For example, a person who signs away the deed to a house, thinking that the document signed was only a guarantee for another person's debt, might be able to plead non est factum in a court and on that basis get the court to void the contract.

Non est factum – Latin for "it is not [my] deed" – is a doctrine in contract law that allows a signing party to escape performance of the agreement. A claim of non est factum means that the signature on the contract was signed by mistake, without knowledge of its meaning, but was not done so negligently. A successful plea would make the contract voidable.