Rate limits - Invoice-AI API

Limit	Applies to	Counted per
120 requests per 60 seconds	Every endpoint except `send`	API key
10 emails per hour	`POST /invoices/{id}/send`	API key
50 emails per hour	Every invoice email, from the API or the dashboard	Account

Every authenticated response includes these headers for the key’s bucket:

Header	Value
`RateLimit-Limit`	The limit for this bucket
`RateLimit-Remaining`	Requests left in the current window
`RateLimit-Reset`	When the window resets, as a Unix timestamp in seconds

Handle a 429

Over a limit, you get 429 rate_limited with a Retry-After header in seconds. Wait that long, then retry with the same Idempotency-Key.

{
  "type": "https://invoice.horizonpay.co/problems/rate-limited",
  "title": "Too many requests",
  "status": 429,
  "detail": "Too many invoices emailed in the last hour. Try again in 42 min.",
  "instance": "req_4f0c2a9e8b7d4c1fa3e2b6d9c0e1f2a3",
  "code": "rate_limited"
}

The SDKs wait and retry automatically when Retry-After is 60 seconds or less. For longer waits they raise RateLimitError with retryAfter (Node.js) or retry_after (Python).

Stay under the limits

Use limit=100 on list endpoints.
Use webhooks or the GET /invoices?status=... filters instead of polling single invoices.
Spread large email batches over several hours.