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Billing engine

Billing engine

Production-shaped invoicing core: quote → invoice → discount → settle → chase → refund. All money stored as integer cents.

Concepts

ConceptDescription
InvoiceCharge with line items, VAT, discount, due date
Line itemdescription, quantity, unit_cents, per-line VAT
CouponPercentage or fixed discount with cap and expiry
PaymentSettled, failed or refunded attempt
DunningState machine that escalates unpaid invoices

Invoice lifecycle

draft → pending → paid
              → overdue → failed
              → void
paid → refunded

Quick links

See also: Backend API, Architecture.