Seal (contract law) in the context of "Authentication"

Legal instrument is a legal term of art that is used for any formally executed written document that can be formally attributed to its author, records and formally expresses a legally enforceable act, process, or contractual duty, obligation, or right, and therefore evidences that act, process, or agreement. Examples include a certificate, deed, bond, contract, will, legislative act, notarial act, court writ or process, or any law passed by a competent legislative body in domestic or international law. Many legal instruments were written under seal by affixing a wax or paper seal to the document in evidence of its legal execution and authenticity (which often removed the need for consideration in contract law). However, today, many jurisdictions have abolished the requirement for documents to be under seal in order for them to have legal effect.

A power of attorney (POA) or letter of attorney is a written authorization to represent or act on another's behalf in private affairs (which may be financial or regarding health and welfare), business, or some other legal matter. The person authorizing the other to act is the principal, grantor, or donor (of the power). The one authorized to act is the agent, attorney, or in some common law jurisdictions, the attorney-in-fact.

Formerly, the term "power" referred to an instrument signed under seal while a "letter" was an instrument under hand, meaning that it was simply signed by the parties, but today a power of attorney does not need to be signed under seal. Some jurisdictions require that powers of attorney be notarized or witnessed, but others will enforce a power of attorney as long as it is signed by the grantor.

In contract law, a simple contract, also known as an informal contract, is a contract made orally, in writing, or both, 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.

In his Commentaries on the Laws of England William Blackstone observed 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.