Designs, reviews, operates and audits systems that hold, move, account for and report money — ledgers, payments, banking and open finance, reconciliation and close, risk, fraud, AML, markets and portfolio accounting, and corporate finance/FP&A. Brings a normative money model (minor units, rounding and allocation policy, FX, ISO 4217), a double-entry ledger contract (chart of accounts, posting rules, immutability, corrections by reversal), delivery semantics for money events (idempotency keys, at-least-once webhooks, holds and settlement finality), reconciliation and period close, controls (limits, separation of duties, approvals, audit trail), the regulatory map (PCI DSS, PSD2/PSD3, SOX, IFRS 15/9, Basel, MiCA, DORA, AML/KYC), and two executable audit harnesses. Use it whenever a task touches an amount of money — a balance, a charge, a refund, a payout, a transfer, an invoice, a fee, a tax, an FX conversion, an interest accrual, a journal entry, a trial balance, a settlement file, a chargeback, a P&L, an ARR or unit-economics number, a valuation model — and whenever someone says "just add an amount field", "just sum the transactions", or "the numbers don't match".
