Charge a late-payment fee when statements are generated so the customer's
receivable reflects it (the gap ERPNext Dunning leaves — it never
increases AR). The fee is billed as a submitted Sales Invoice (item ->
Dunning Type income account, rate = computed fee) rather than a Journal
Entry, so the app's existing payment flow (Run Payment / AutoPay /
multi-invoice) charges and settles it automatically via its Sales Invoice
references — a bare JE would sit uncollected.
Fee schedule/amounts come from the existing Dunning Type settings (yearly
rate_of_interest + flat dunning_fee), interest computed with ERPNext's own
Dunning formula. The fee Item is configured via a new Late Fee Item custom
field on Dunning Type (created in an after_migrate hook; ns_app/setup.py).
Nothing is auto-seeded: generation stops with a clear error if no Dunning
Type is configured or its income account / fee item is unset.
Billing is idempotent per customer/company/month, and prior fee invoices
are excluded from the interest base (no fee-on-fee). The fee invoice shows
on the statement flagged 'late fee', folded into Total Due (which equals
the customer's balance and is fully collectible).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Norman King
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