Overview
The KSeF TEST environment (api-test.ksef.mf.gov.pl) is the Ministry of Finance's sandbox where you can send FA(3) invoices without touching production data. It uses the same FA(3) schema and the same status flow, so it is the safe place to validate your XML, your authentication and your status handling before going live. Notaly's sandbox maps to KSeF TEST and includes three free test invoices.
What TEST is for
KSeF (Krajowy System e-Faktur) is Poland's national e-invoicing platform run by the Ministry of Finance (Ministerstwo Finansów). The TEST environment mirrors the production API: you generate a test token, open a session, send an encrypted FA(3) invoice and read back a status with a UPO or a rejection code. Because the schema is identical, an invoice that passes in TEST is much more likely to pass in production — which is exactly why you should never skip this step.
TEST vs production
The two environments are separate. They have different endpoints and different credentials, and a test invoice has no production or tax effect. The FA(3) schema is the same, so the value of TEST is not in "practice data" but in catching schema errors, authentication mistakes and status-handling bugs before they cost you a real customer invoice.
How to test with Notaly
Sign up for the sandbox — no KSeF token needed: the sandbox submits to KSeF TEST with Notaly's own test credentials, so use the sandbox seller NIP 2745013933 in your payload. Then send a test invoice through POST /invoices; Notaly generates the FA(3) XML, validates it against the official XSD, authenticates to KSeF TEST and returns the status and UPO by webhook. You get three free test invoices, which is enough to confirm your payloads, your NIP data and your webhook handling end to end.
What to check before going live
Confirm the seller and buyer identifiers, the line items, and that you can read both accepted (with UPO) and rejected statuses from the webhook. Once the TEST flow works, upgrade to a paid plan and connect your own production KSeF token in Connect KSeF (NIP + token); once production is enabled, Notaly routes your invoices to KSeF production — and the sandbox stays available for staging.
Disclaimer
Notaly is not a tax, accounting or legal advisor. This article is general information, not tax advice, and may be outdated. You are responsible for your own VAT compliance; confirm with a qualified accountant where required.
Sources
Source: www.podatki.gov.pl