Terms of Use
Last updated: March 2026
ksefuj.to is a free, open-source tool for validating KSeF FA(3) invoices. By using this tool, you accept the following terms.
1. Open Source License (Apache 2.0)
The source code of ksefuj.to is released under the Apache 2.0 license. You may freely use, modify, and distribute it — including commercially — provided you retain copyright and license notices and indicate any changes made. The license is available on GitHub.
2. No Warranties
The tool is provided "as-is", without any warranties — express or implied. We do not guarantee that the validator will catch every error, or that validation results will be complete or free of mistakes.
3. Limitation of Liability
ksefuj.to is not tax or legal advice. The authors are not responsible for errors in invoices, KSeF submission problems, tax penalties, or any other losses resulting from use of the tool. Final responsibility for invoice correctness rests with the user.
4. User Responsibility
You are responsible for verifying the correctness of your invoices before submitting them to the KSeF system. The tool helps detect common errors, but does not replace verification by an accountant or your own knowledge of applicable regulations.
5. Free Forever
The validator on ksefuj.to is and will remain free — no limits, no hidden costs, no user accounts, no paywall. We believe essential validation tools should be accessible to everyone working with KSeF.
6. Privacy
Your XML files never leave your browser. All processing happens locally — no invoice data is sent to any server. See the Privacy Policy for details.
7. Governing Law
These terms are governed by Polish law. Any disputes will be resolved by the competent Polish courts.
8. Contact
Questions about these terms? Contact us at: [email protected]