Skip to content
What Is KSeF?
KSeF (Krajowy System e-Faktur) is Poland’s National e-Invoicing System operated by the Ministry of Finance. It is a central platform for issuing, receiving, and storing structured electronic invoices. KSeF replaces traditional paper and PDF invoices and will become mandatory for most VAT-registered businesses from 2026.
The system ensures transparency, faster tax control, and standardized invoicing across Poland.
Frequently Asked Questions About KSeF
1. When Will KSeF Become Mandatory?
The obligation to use KSeF will be introduced in stages:
- From February 1, 2026 – for large taxpayers
- From April 1, 2026 – for all other VAT taxpayers
From these dates, most invoices must be issued in structured XML format via KSeF.
2. What Is a KSeF Invoice Number?
Every invoice approved by KSeF receives a unique identification number. This number becomes the official reference for the document and will often be required for accounting, payments, and legal purposes.
From August 2026, the KSeF number may also be required in payment titles.
3. Can KSeF Invoices Include Attachments?
Yes. KSeF allows the use of attachments that form an integral part of the invoice, such as technical documentation or detailed VAT calculations.
To use attachments, businesses must submit a special request through the Polish e-Tax Office (e-Urząd Skarbowy).
4. How Can I Download Invoices from KSeF?
Invoices can be retrieved in two main ways:
- Through the official KSeF application after logging in
- Via external accounting systems that automatically synchronize invoice data
Most modern accounting platforms provide built-in KSeF synchronization.
5. Are B2C Invoices Required in KSeF?
Invoices issued to private individuals (B2C) are not always mandatory in KSeF. In many cases, their submission remains optional, although businesses may still choose to send them through the system.
This depends on the taxpayer’s status and specific regulations.
6. How Do Correction Invoices Work in KSeF?
Correction invoices for documents issued in KSeF must include:
- The original KSeF invoice number
- Detailed information about changes
- Updated tax and transaction values
All corrections are registered and archived within the system.
7. What Happens If KSeF Is Temporarily Unavailable?
In case of system outages or connectivity issues, businesses may issue invoices in offline mode.
However, these invoices must be uploaded to KSeF immediately after system access is restored. Failure to do so may result in penalties.
Summary: Key KSeF Rules for Businesses
KSeF is no longer a future concept—it is a legal requirement approaching rapidly. From 2026, most Polish businesses issuing VAT invoices will be required to:
- Use structured XML invoice formats
- Submit invoices via KSeF
- Store documents in the central system
- Ensure full technical compliance
Early preparation helps avoid operational disruptions and financial penalties.
KSeF Integration with WordPress and WooCommerce
If you run an online store or service website based on WordPress or WooCommerce, KSeF compliance requires proper technical integration.
The safest approach is to connect your website with accounting platforms such as:
These platforms validate invoices before submitting them to KSeF, reducing the risk of errors.
Professional integration ensures:
- Automatic invoice creation
- Secure API communication
- Error validation
- Backup and archiving
- Compliance monitoring
Need Help Implementing KSeF in Your Business?
If you want to prepare your WordPress or WooCommerce website for KSeF in a secure and future-proof way, I can support you with:
✔ Technical analysis ✔ System selection ✔ API integration ✔ Testing and validation ✔ Staff training ✔ Ongoing support
Contact me to make sure your business is fully compliant with Poland’s e-invoicing regulations before 2027.
