Letters close (Latin: litterae clausae) are a type of legal document which is a sealed letter issued by a monarch or government granting a right, monopoly, title, or status to an individual or to some entity such as a corporation. These letters were personal in nature, and were delivered folded and sealed, so that only the recipient could read their contents. This type of letter contrasts with the better-known letters patent.
It was necessary to break the seal in order to open and read the letter, and so its arrival with the seal intact showed that it had not been intercepted or tampered with. However, once the seal was broken, it could no longer confirm the authenticity of the document. The original charters of Edward the Confessor can be considered to be a form of letters close, as they were delivered wrapped, with the seal hanging down.
This type of letter later developed into the formal business letters that we are familiar with today.
It is thought that the earliest surviving example of an English royal letters close remaining unopened dates to the reign of Henry VIII. In England these letters are typical of those generated by the developing state bureaucracy. From 1204, copies of English letters close transcribed onto the Close Rolls are extant. However, examples of actual letters close, as opposed to the recorded copies in the Close Rolls, are extremely rare, and most of those exist because King Henry II required the return of some to the government.
Another example of letters close is Papal Letters close. These often had the leaden papal bulla attached to the letter with a hemp cord, in contrast to the fine silk cords used for higher grades of document. The cords were often threaded through the letter to keep it folded, with the address written on the dorse (back) of the document so that it could still be read.