invoice_write_off_not_permitted
billing.invoice.write_off invoked against an invoice whose tenant's commercial_status is comped or internal. mark_uncollectible books to Bad debt, which says cash was expected and the customer failed us; a comp says no cash was ever expected and the customer is in good standing. Coded as bad debt the tenant enters delinquency reporting and the 11-billing.md §Dunning ladder - launches blocked at day 7, outbound suspended at day 14 - which is the single worst thing this platform could do to the customer it is trying hardest to keep. What an operator does: issue a credit note instead (billing.credit_note.issue). P2, unbuilt.
Problem shape
Every non-2xx response is an RFC 9457 application/problem+json body. The type URI below is stable and machine-matchable, so branch on the final path segment (the code) and treat the status as redundant confirmation. See the error-handling guide.
{
"type": "https://docs.vocapable.com/errors/invoice_write_off_not_permitted",
"title": "…",
"status": 409,
"detail": "…",
"instance": "/v1/…"
}