Collections & arrears
Arrears, and metered input — invoices and balances come from the ERP.
Invoices and balances are read from the ERP layer; saving a reading posts to it and flows back to the customer.
Self-serve payment plans are not yet backed by a system — this is a non-functional placeholder, shown for intent only.
A posted reading appears as a new invoice on the customer's billing surface in the same session.