billing-money-rules

name	billing-money-rules
description	Use when creating or editing code under services/billing. Enforces Helpline's money-handling rules — integer cents only, seat limits, and BillingError for every violation.
paths	services/billing/**

Billing money rules

This skill activates when work is happening in services/billing. It exists so money bugs never ship.

The rules (load these every time)

1. Money is integer cents. Never a float, never dollars. Variables and fields end in _cents.
2. Plan economics live in one place — _SEAT_LIMITS and _PRICE_PER_SEAT_CENTS in subscriptions.py. Never hard-code a price or a limit anywhere else.
3. Every money/plan violation raises BillingError (HTTP 402). Never silently clamp seats, skip a charge, or return a partial result.
4. Inactive subscriptions cannot be invoiced.

When you need the detail

For the full rationale, edge cases, and worked examples, read references/money-conventions.md. Only load it when a change is non-trivial — the four rules above cover most edits.