The transition began with the shutdown of the KSeF 1.0 Test environment on September 1, 2025. shutdown of the KSeF 1.0 Test environment on September 1, 2025. Subsequently, the KSeF 2.0 Test environment will open for API testing on September 30, 2025, followed by the Pre‑production (Demo) environment opening on October 15, 2025. Accordingly, testing will not be possible until late September, when t…