In Germany, a contract to sell a piece of land must be recorded by a notary. The Civil Code says so in § 311b. A sale agreed on a handshake, or in a letter signed by both sides, is void, however clearly both of them wanted it. The general rule is § 125: Ein Rechtsgeschäft, welches der durch Gesetz vorgeschriebenen Form ermangelt, ist nichtig. A legal transaction that lacks the form prescribed by law is void. The law offers one way back. The contract becomes valid after all once the transfer has been declared and entered in the land register.