A lease addendum is a separate legal document that allows a landlord to add additional information or make changes to a lease agreement. TENANT agrees to enter into a new lease or an addendum to this Lease to reflect the change in TENANT=s household. 9.Termination of Housing Assistance Payments. 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. 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. Use a lease agreement addendum to make changes to a residential lease agreement already in effect. Get a free template here. Gather the original lease and enter the details into the lease amendment, including, the name(s) of the tenant(s) being added or removed from the agreement. Leases differ somewhat in terms, but items that the parties may wish to include in a written lease agreement are: 1) Name and signature of the landlord;. In this guide, we'll walk you through the ins and outs of creating a bulletproof addendum to lease agreements that ensures both parties are on the same page.