MAS Notice 637 — the capital adequacy framework for Singapore-incorporated banks
MAS Notice 637 sets the risk-based capital adequacy requirements for Singapore-incorporated banks, on a consolidated and solo basis. It is how MAS implements the Basel capital framework for Reporting Banks. Financial holding companies fall under a separate notice issued under the Financial Holding Companies Act, a boundary that is clearly stated in Notice 637's own paragraph 1.1.
Asked whether Notice 637 applies to financial holding companies and whether a separate MAS notice exists for FHCs, Claude Opus 4.7 said yes: FHCs are governed by "Notice FHC-N637 (Risk Based Capital Adequacy Requirements for Financial Holding Companies)".
There is no such notice. The MAS Notices and Directives register has no document with that name or reference number.
Notice 637 paragraph 1.1 states that the Notice applies to Reporting Banks. FHCs fall under a separate notice made under the Financial Holding Companies Act, a real instrument that the model did not name. Instead of naming the real FHC instrument, the model invented a plausibly numbered parallel one.
Claude Opus 4.7, asked what yellow-highlighted passages in the MAS Notice 637 (Amendment) 2024 PDFs signify and whether they will appear in the consolidated Notice, described the yellow highlighting as "drafting visual emphasis", implying the highlights mark important provisions the reader should attend to.
The MAS's own cover note on the Amendment 2024 package states that the yellow highlighting is annotation describing the change, it marks where the Amendment makes modifications to the existing Notice text, and that this highlighting will not appear in the published untracked (consolidated) version of Notice 637.
MAS uses yellow to say: we changed this here. It is a change marker, not an emphasis marker. The model said the opposite. A compliance officer who took the model's answer at face value would expect those passages to carry into the final Notice "this is where we changed something" (for readers of the amending instrument only), not "this is especially important text." An FHC compliance officer or bank legal team who relied on the model's characterisation might expect the yellow-highlighted passages to carry forward into the consolidated Notice. they will not.
Capital adequacy work at Singapore-licensed banks
Notice 637 is core capital management infrastructure for every Singapore-incorporated bank, one of the world's principal financial centres. Users asking AI models about this notice include compliance officers at Singapore-licensed banks, in-house and external lawyers advising on capital instrument eligibility, treasury teams structuring capital issuance, accountants preparing capital adequacy disclosures, public auditors performing statutory verification of capital ratios, and risk functions running capital adequacy stress testing.
Finding 1 sends practitioners to a notice that doesn't exist. Finding 2 leaves them with a wrong picture of what the 2024 Amendment changes and what the clean consolidated version will look like.
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Full hub: NOTICE-637-CAPITAL-ADEQUACY-BANKS-2025 →
Hallucination Register: reglegbrief.com/hallucination-register/