As a rule, contracts and declarations of intent do not require any special form. In particular, contracts do not generally have to be concluded in writing. A handshake is also sufficient to establish an effective contractual relationship. Nevertheless, for reasons of preserving evidence and documentation, it is advisable to conclude contracts in writing. In addition, agreements are often made according to which certain declarations or notifications are subject to the written form, and for some specific forms of contract or declarations of intent this is even required by law. This is primarily for the purposes of documentation and verifiability with a view to any subsequent legal disputes.