invoice_conflict

HTTP 409

The invoice conflicts with one already recorded.

Response shape

{
  "type": "https://cogdepot.com/problems/invoice_conflict",
  "title": "<short human-readable summary>",
  "status": 409,
  "detail": "<what happened on this occurrence>",
  "reason": "invoice_conflict"
}

Branch on reason. The title is prose and may be reworded; reason is the stable contract.