Guides

Status, changes and support

Where the API stands, how we version it, where to follow changes and how to get help fast.

API status

The API is in early access: test mode with KSeF TEST is available, and we hand out keys in batches to people on the launch list. Live mode comes later; we will tell participants the date. There is no public status page yet: we inform participants about planned downtime and incidents by email.

When KSeF does not answer, you need to do nothing: invoices wait in the queue and are sent automatically (ksef_unavailable).

Versions

Every response carries a KSeF-Api-Version header with the version date (currently 2026-10-19). Without notice we only make backwards-compatible changes: new response fields, new event types and new error codes. Write code that ignores unknown fields and treats an unknown error code like a generic error of its type. Breaking changes will be announced by email in advance and get a new version date.

Changelog

Every change to the app, the API and the site goes into the changelog. The OpenAPI specification is always available in its current version: openapi.yaml.

Technical support

Write to kontakt@ksefshop.pl. To get help fast, include:

• the Request-Id response header (e.g. req_8Kq2Lm4Np6Rs8Tu0Vw2X),
• the invoice or correction id (inv_..., cor_...) and the mode (test or live),
• the error code and the time of the request.

Never send us a full API key or webhook secret. The first characters are enough, e.g. sk_test_4f....