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Credit card facility engine
ID MOD-167
System SD05
Repo bank-credit
Build status Not started
Deployed No

What this module does

Credit card facility engine. Manages the full lifecycle of a revolving credit card facility from opening through to closure: balance tracking, billing cycles, interest accrual, minimum repayment calculation, statement generation, and the real-time JIT-funding webhook that sits in the card-authorisation path.

This module ID is reserved per ADR-058 (credit card platform boundary). It is not built until a credit card product is formally greenlit by the CEO/Board (ADR-058 Phase 2).

Why it exists

ADR-058 established the credit card platform boundary and determined that the credit card facility engine is the only substantive new platform module required to launch a credit card programme. All other boundary decisions — scheme/processor abstraction (PAY-008), physical card records (MOD-124 credit-ready columns), and credit decisioning (MOD-029/031) — have already been addressed as pre-work.

The module ID is reserved here so that cross-references in ADR-058, PAY-008, and MOD-124 (credit_facility_id column) are stable and do not drift to an unrelated module if the number is allocated in the interim.

Responsibilities

When built, this module owns:

  • Facility management — open, limit changes, suspension, closure of revolving credit facilities. Maps to a credit.loan_accounts row with product_type = 'CREDIT_CARD'.
  • Balance tracking — real-time available credit = facility limit − outstanding balance − pending authorisations.
  • Billing cycle engine — monthly cycle cut, statement balance, minimum repayment calculation per NZ and AU regulatory requirements (minimum of 2% of outstanding or $25, whichever is greater, per jurisdiction rules).
  • Interest accrual — daily interest on the revolving balance at the applicable rate; posted via MOD-001 posting_type = 'ACCRUAL'.
  • JIT-funding webhook — the only platform component sitting in the sub-100ms card-authorisation path. Receives authorisation requests from the issuer-processor, checks available credit in-process (no external I/O in the response path), and responds with approve/decline. Performance target: p99 < 80ms under steady-state load (PAY-008 mandate).
  • Statement generation — monthly statements via MOD-113 (or internally until MOD-113 is extended for the credit card asset class).
  • Minimum repayment reminders — dispatched via MOD-063 at billing cycle close.
  • IFRS 9 integration — revolving balance feeds MOD-031 ECL calculation as the EAD for the CREDIT_CARD product type.

Pre-work already done (ADR-058)

The following changes were made before this module is built:

  1. MOD-124 — payments.physical_cards extended with card_type = 'credit' option, credit_facility_id UUID (links to this module's facility record), and bin_range_type (sponsor | principal).
  2. PAY-008 — Card scheme abstraction policy extended with processor-neutral interface, scheme-neutral BIN range configuration, JIT-funding webhook p99 < 80ms mandate, and processor-switch covenant (PAN/token portability as RFP non-negotiable).

What triggers the build

A formal credit card product greenlight decision by the CEO/Board, followed by selection of an issuer-processor and card scheme. ADR-058 Phase 2 is the trigger. Until then this module remains Not started and deployed: false.

Design notes (pre-greenlit)

  • Follows the MOD-117 (overdraft management) pattern for revolving product management within the SD05 credit domain.
  • The JIT-funding webhook must be architecturally isolated from the rest of the module — it must not share a Lambda with any path that calls external services (database reads should be warm-cache or in-memory for the authorisation response).
  • NZ and AU minimum repayment rules differ; jurisdiction-aware billing cycle logic is required from day one.
  • BIN range sponsorship is a distinct credit-card-specific relationship from the debit/eftpos sponsorship (PAY-008 §BIN range sponsorship). This requires separate negotiation with a sponsor bank that holds credit-card BIN sponsorship capability.

Module dependencies

Depends on

Module Title Required? Contract Reason
MOD-001 Double-entry posting engine Required — All credit card postings — purchases, repayments, interest accruals, fee charges — are written to the double-entry ledger via the posting engine.
MOD-029 Pre-approval engine Required — Credit card origination requires a credit assessment and affordability check before a facility is opened.
MOD-031 ECL calculation & GL posting Required — Credit card revolving balances contribute to portfolio ECL; MOD-031 reads credit.loan_accounts to compute provisions for the credit card asset class.
MOD-124 Physical card issuance and bureau integration Required — Physical card records carry credit_facility_id linking the card to its MOD-167 facility, and card_type='credit' set at issuance.
MOD-005 Daily accrual calculator Optional — Daily interest accrual for revolving balances; v1 may compute accrual internally following MOD-005 pattern rather than depending on the shared accrual engine.
MOD-113 Statement generation Optional — Monthly credit card statements generated via the statement engine; v1 may generate statements internally until MOD-113 is extended for the credit card asset class.

Required by

(No modules in this wiki currently declare a dependency on this module.)

Policies satisfied

Policy Title Mode How
CRE-001 Credit Risk Management Policy AUTO Credit card revolving facility balance and utilisation are tracked per customer account with full audit trail for credit risk reporting.
CRE-006 Impairment & Provisioning Policy CALC Credit card asset class contributes to IFRS 9 ECL calculations — revolving balance is the EAD; product-type LGD and PD are applied by MOD-031 once MOD-167 feeds the credit.loan_accounts table.
CON-004 Product Disclosure & Sales Practice Policy GATE Minimum repayment disclosures and billing-cycle statements are gated on delivery confirmation before the next billing cycle opens.
PAY-008 Payment Routing, Sponsor & Card-Scheme Abstraction Policy AUTO JIT-funding webhook responds to issuer-processor authorisation requests within p99 < 80ms by querying available credit in-process with no blocking external I/O.

Capabilities satisfied

(No capabilities mapped)

Part of SD05 — Credit Decisioning & Loan Platform Compiled 2026-05-22 from source/entities/modules/MOD-167.yaml