A promissory note must contain all of the following EXCEPT:

1. Section 4 — a promissory note requires (a) unconditional undertaking, (b) signed instrument, (c) sum certain, (d) payable to or to the order of a person or bearer. 2. Attesting witnesses are NOT a statutory requirement of a promissory note. 3. Hence (C). _Source: ICAI BoS CA Inter Paper 2 — Negotiable Instruments Act 1881_