An addendum can clearly spell out what is allowed and any special requirements to return the home to found condition upon move out. A lease addendum is a separate legal document that allows a landlord to add additional information or make changes to a lease agreement.In an addendum to a lease, you will need to add the dates, names and addresses of all parties involved in the original lease agreement. Return to form category list. 2. When compiling the legal paperwork to add a tenant to a lease, you can create an addendum to the existing lease or create a new lease agreement. You should include the date, the rental property address, and the names of each party just as you would in the original lease. A lease extension addendum is a legal document extending a lease between a landlord and a tenant. In the middle of the agreement: Tenants might be able to decline to sign it if it is an addendum to a current lease. Either party can initiate the process of extending a lease agreement using an addendum. 1. Contact the Landlord.