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. A lease addendum is a separate legal document that allows a landlord to add additional information or make changes to a lease agreement.Use a lease agreement addendum to make changes to a residential lease agreement already in effect. Get a free template here. A lease addendum is as important as the rest of the lease. 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. 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. Fill Out the Date: Write the specific date when the addendum is created. A Massachusetts rental agreement is a formal contractual agreement between landlords and tenants for leasing a property in the state. MASSACHUSETTS RENTAL VOUCHER PROGRAM (MRVP) a.