Realm latefees publishes a graduated late-fee penalty on an overdue invoice held in the live r/invoices. A creditor (an invoice issuer) declares a late-fee SCHEDULE once — a p/tiers schedule over how many blocks an invoice is overdue — and the realm prices the penalty as a function of that overdue duration, escalating by tier. The penalty can be read live (PenaltyNow) or frozen into a sequence-numbered ASSESSMENT the creditor can point a payer to.
It is the fourth consumer of p/tiers and the one that exercises its "progressive fee" reading over TIME rather than quantity: r/meters prices usage, r/payslips prices withholding, and this prices lateness. It is the second consumer of r/invoices after r/receivables, and reads the exact integration surface that realm's header advertises — invoices.InvoiceInfo, invoices.IsOverdue, invoices.HasInvoice — all non-crossing views, no struct slice crossing a realm boundary.
It is a PUBLISHER, not a collector
r/invoices is live and immutable, so this realm CANNOT add a charge to an invoice there, and it holds no coins of its own — no banker, no deposit, no payout, no withdrawal path. A published penalty is a verifiable CLAIM backed by the invoice's own facts and the creditor's declared schedule, exactly as r/receivables publishes a loss provision and r/cashflow a statement. It compels nothing; a debtor who ignores a late fee is in the same position as one who ignores the invoice. A custodial variant that collects the fee is a separate, larger product and is deliberately out of scope.
The pricing axis, and the one it is not
The base handed to p/tiers is the OVERDUE DURATION in blocks (`now - dueHeight`), and each tier's rate is a ugnot accrual per RateScale blocks. So the penalty ESCALATES WITH TIME: the longer an invoice is overdue, the higher the marginal accrual. p/tiers' rate cap makes `penalty <= overdueBlocks` an arithmetic fact — the fee can never exceed one ugnot per overdue block, a natural ceiling.
It is NOT a percentage of the outstanding amount. p/tiers prices one amount against breakpoints — a single dimension — and a fee that is both time-escalating AND balance-scaled is two dimensions it cannot express in one call. The creditor scales the ugnot accrual to their debt magnitudes through the schedule; the assessment records the outstanding beside the penalty so a reader can compute an effective rate. Composing a balance- scaled fee as a single Charge call would be a plausible, wrong number.
The trust boundary, inherited twice over
A penalty is a self-report of a self-report of a self-report: the issuer set the invoice amount in r/invoices, the due height there, AND the late-fee schedule here. This realm computes faithfully from those; it does not validate that any of them is fair. A creditor may only assess their OWN invoices — Assess derives the issuer from `cur.Previous().Address()` and reads invoices.InvoiceInfo under that key, which returns only invoices that address issued.
