Promissory Note (Section 4): Written unconditional promise to pay fixed sum to specified person. Elements: (1) Written form; (2) Unconditional promise; (3) Fixed amount; (4) Payee identification; (5) Maker signature. Parties: Maker (drawer), payee. Maker liable; cannot contain conditions. For accountants, promissory notes common in credit transactions; understanding requirements critical for valid enforcement.