Error codes

HTTP code	Meaning
200	Success
400	Bad Request — validation or missing field
401	Unauthorized — invalid Bearer token / API key
403	Forbidden — user not a member of the company
404	Not Found
409	Conflict — duplicate resource
429	Too Many Requests — rate limit
498	Token expired — refresh access token
500	Internal Server Error — contact support

Common error response format

{
  "message": "ERROR",
  "errors": [
    "Invoice XML size must be between 1 byte and 10MB"
  ],
  "trackingId": "uuid"
}