How long will it take? Most people complete each MPN in less than 30 minutes.Our attorneys have decades of experience representing registered representatives in promissory note defense cases in the FINRA arbitration forum. How do you create a Promissory Note? The Master Promissory Note (MPN) is a legal document in which you promise to repay your loan(s). It also explains the terms and conditions of your loan(s). Attorneys who represent the successful party must prepare a judgment and submit it to the judgment clerk for review. Writing a promissory note should be tailored to your specifications of that particular loan. Check out a free preview of a promissory note at 12Law. Complete Master Promissory Note (MPN).