Contact your loan servicer for more information before you complete the application. A promissory note is less common in construction, but when used effectively it can be a helpful addition to a collection toolbox.Most people complete each MPN in less than 30 minutes. The entire MPN process must be completed in a single session. A promissory note is a written promise, basically an IOU, to pay money to someone. The note document serves as written evidence of the debt.