A Lease Addendum is a document used to modify or supplement an existing lease agreement. It is an amendment to a lease agreement that adds, deletes, revises, or otherwise changes the terms and conditions of the original lease. A Lease Addendum can also be used to add a tenant, extend the lease term, alter the rental amount, or add a clause allowing for an early termination. There are several types of Lease Addendums, including Pet Addendums, Security Deposit Addendums, Parking Addendums, and Sublet Addendums.