memorandum

Definition from Nolo’s Plain-English Law Dictionary

Any written record, including a letter or note, that proves that a contract exists between two parties. This type of memo may be enough to validate an oral (spoken) contract that would otherwise be unenforceable because of the statute of frauds. (Under the statute of frauds, an oral contract is invalid if it can't be completed within one year from the date the contract is made.)

Definition provided by Nolo’s Plain-English Law Dictionary.