Montana Amendment Addendum is an amendment to a contract that is specific to the state of Montana. It is a legal document that is used to modify or add specific terms, conditions, or clauses to an existing contract without changing the original agreement between the parties. Types of Montana Amendment Addendum include residential, commercial, and agricultural amendment addendums. The amendment addendum must be signed and dated by all parties involved in the contract in order for it to be legally binding. The amendment addendum must also include the specific changes that are to be made to the contract and the effective date of the addendum.