Use our free, attorneycrafted Washington Promissory Note template. Find out what's included in the agreement and how to write it.CURRENCY: All principal and interest payments shall be made in lawful money of the United States. 7. Review any notes that the client or their financially responsible AU member owns. Accept and consider evidence as to the FMV of the note. A promissory note need only be signed and does not require an acknowledgement before a notary public to be valid. When to Use a Promissory Note. You don't need an attorney to write a Washington promissory letter. Simply download the relevant form and fill out the required information. Complete your Master Promissory Note (MPN) to acknowledge that you understand the terms and conditions of your federal student loans.