In common law, a deed is any legal instrument in writing which passes, affirms or confirms an interest, right, or property and that is signed, attested, delivered, and in some jurisdictions, sealed. It is commonly associated with transferring (conveyancing) title to property. The deed has a greater presumption of validity and is less rebuttable than an instrument signed by the party to the deed. A deed can be unilateral or bilateral. Deeds include conveyances, commissions, licenses, patents, diplomas, and conditionally powers of attorney if executed as deeds. The deed is the modern descendant of the medieval charter, and delivery is thought to symbolically replace the ancient ceremony of livery of seisin.

The traditional phrase signed, sealed and delivered refers to the practice of seals; however, attesting witnesses have replaced seals to some extent. Agreements under seal are also called contracts by deed or specialty; in the United States, a specialty is enforceable without consideration. In some jurisdictions, specialties have a liability limitation period of double that of a simple contract and allow for a third party beneficiary to enforce an undertaking in the deed, thereby overcoming the doctrine of privity. Specialties, as a form of contract, are bilateral and can therefore be distinguished from covenants, which, being also under seal, are unilateral promises.