Civil Law Act (Cap. 43): Primary legislation governing contractual obligations and enforceability in Singapore. Contains key provisions regarding interest rates and consideration requirements for contracts.

Contracts (Rights of Third Parties) Act: Legislation governing how third party rights may be affected by contractual arrangements, which may be relevant if the promissory note impacts parties other than the primary signatories.

Moneylenders Act (Cap. 188): Regulates moneylending activities in Singapore, particularly important for interest-bearing promissory notes to ensure compliance with usury laws and lending regulations.

Bills of Exchange Act (Cap. 23): While primarily focused on bills of exchange, this Act provides important framework provisions regarding negotiable instruments including promissory notes.

Housing Development (Control and Licensing) Act: Relevant property law especially if the down payment relates to residential property purchase, governing developer-buyer relationships and payment arrangements.

Limitation Act (Cap. 163): Sets statutory time limits for enforcement of contractual claims, generally providing a 6-year limitation period for promissory notes.

Money and Currency Act: Governs currency denomination and payment terms in Singapore, ensuring proper specification of monetary obligations in legal documents.