How To Write A Legally Binding Letter . If your lease lists other addresses or methods of communication, use those as well. So it’s best to consider the letter of intent more as a notice, a consolidation of terms and an update. Free Legally Binding Loan Agreement Template from soulcompas.com Include the exact dates when the related people or companies interacted. The date of the declaration, and the names of your executors or trustees. Legally binding requires both party’s signatures on a document.