The Negotiable Instruments Act, 1881 governs promissory notes, bills of exchange, and cheques. Introduction: Negotiable instrument is written document containing unconditional promise/order to pay fixed sum. Key provisions: Sections 1-154 cover definitions, types, negotiability, liability, and remedies. Features: Negotiability (transfer by endorsement), transferability (successive owners), limited defenses. For accountants, understanding NI Act critical for cheque processing, bank reconciliation, and credit transactions.