Texas Mortgage Modification Laws. In Texas, you can make an agreement called a mortgage modification with your lender to modify the existing terms of your loan.A loan modification agreement is used when a lender and borrower elect to modify the terms of a pre-existing promissory note. A real estate attorney can prove your inability to repay the mortgage, which increases the chances of getting a reduction in the interest rates. The mortgage modification agreement is a legal document between a lender and borrower to change an existing loan's terms. Defining the details of a loan modification agreement is essential for any successful process. Our free templates and this guide can help you get started. Documents to be prepared for you: "Follow-Through" Instructions, Modification Agreement. Step 1: Fill out your court forms. Fill out the following starting forms: â—‹ Petition to Modify the Parent-Child Relationship.