Many landlords and landlords prefer to use a simple lease and use nachtrage to adjust their lease per tenant. Specify the place to write the date on which the endorsement is executed. Also prepare lines to allow interested parties to write their full names at the same time as their signatures. Finally, to make the contract legitimate, you should leave room for a notary`s stamp, as well as the date and signatures of the parties involved. Buyers and sellers should receive a copy of the original sales contract. You need to check and find the effective date to be able to refer to the agreement in the addendum. A supplement to a contract is used to update or modify an existing contract, which is often the case for business relationships. Cancelling and creating a new contract is not ideal considering the cost and time it would take to make this change.