/ˈmjuːtʃuəl mɪsˈteɪk/ – Phrase
Definition: Cả hai bên đều mắc lỗi.
A more thorough explanation: a situation where a contract can be made void (=said not to exist) because both of the parties to the agreement were mistaken about the same material fact concerning the contract
Example: Although the sale was made under “mutual mistake of fact,” the sales tax was lawfully collected and will not be refunded.