# Invoice email daily limit returns 429 instead of 500 from 2027-01-14

- **Provider:** Xero
- **Endpoint:** `POST /api.xro/2.0/Invoices/{InvoiceID}/Email`
- **Effective:** 2027-01-14
- **Severity:** medium
- **Change:** status-code
- **Status:** verified

## What changed

From 2027-01-14, POST Invoices/{InvoiceID}/Email returns 429 Too Many Requests instead of a generic 500 when the organisation reaches its daily invoice-email limit. The 429 has no Retry-After header. Code that treats 500 as a retryable server error, or retries a 429 at once with a short backoff, will mishandle the limit.

## What to do

Handle a 429 from the invoice Email endpoint separately from the per-minute rate limit. It is a daily limit with no Retry-After header, so don't retry immediately. Queue the send for after the daily reset, or tell the user sending was delayed. Stop relying on a 500 to detect this case.

## Sources

- Provider notice (2026-10-15): https://developer.xero.com/changelog
- https://raw.githubusercontent.com/XeroAPI/Xero-OpenAPI/master/xero_accounting.yaml

## Machine-readable

- Advisory: https://github.com/SriVarshini09/shapi-advisories/blob/main/advisories/xero-invoices-email-daily-limit-429.json
- OSV: https://shapi.dev/osv/xero-invoices-email-daily-limit-429.json