Simple contract
In contract law, a simple contract is a contract made orally or in writing or both of them rather than a contract made under seal. Simple contracts require consideration to be valid, but simple contracts may be implied from the conduct of parties bound by the contract. William Blackstone observed in his Commentaries on the Laws of England that in the seventeenth century, debtors used simple contracts as one of three accepted forms of unsecured debt instruments. In 1828, the Parliament of the United Kingdom amended the statute of frauds so that oral acknowledgments or promises could not be used as evidence to prove the existence of a simple contract. Today, some American jurisdictions have established that a security interest is perfected "when a creditor on a simple contract cannot acquire a judicial lien that is superior to the interest" of the secured party.

See also
 New England Mutual Life Insurance Co. v. Woodworth
 Company seal

References 

Common law
Contract law