KSeF for JDG — Complete Guide 2026

Q: What Is KSeF?

KSeF is a Ministry of Finance platform where all invoices are issued, transmitted, and stored in structured form (XML FA(2)). You don't issue an invoice in your own software and send a PDF — the invoice is created inside the KSeF system.

Q: What Does This Change in Practice?

You don't send PDFs — the contractor receives the invoice automatically in their KSeF system The invoice has a KSeF-assigned number — not your own number You deduct costs automatically — invoices from Polish suppliers appear in your KSeF on their own and are ready for VAT deduction The standard audit file (JPK) generates itself — KSeF produces the JPK_V7 file from your invoices

Q: Who Does KSeF Apply To?

From April 1, 2026: All VAT taxpayers — active and exempt from VAT (if turnover is below 200,000 zł) Sole proprietorships (JDG) on lump sum tax (ryczałt), tax scale (progressive), and flat tax 19% — if they are registered as VAT taxpayers or use the subject-matter exemption

Q: How to Issue an Invoice in KSeF — Step by Step

Step 1: Log In to KSeF Log in via Trusted Profile (Profil Zaufany) or e-ID (e-Dowód) at ksef.mf.gov.pl. Step 2: Choose Your Interaction Method You have two options: Interactively — fill out the form directly on the KSeF website (free, but time-consuming) API / integration — your accounting software sends the invoice automatically (requires KSeF integration) Step 3: Fill In Invoice Data A structured invoice requires: Seller and buyer data (NIP, name, address) Issue date and date of sale Line items (name, quantity, net price, VAT rate) Total net, VAT, gross Payment method and due date Step 4: Receive Your KSeF Number After sending the invoice, KSeF assigns it a unique number (the so-called KSeF number). This number must appear on every invoice — it's proof that it was issued correctly. Step 5: The Contractor Receives the Invoice Your contractor sees the invoice in their KSeF system automatically — you don't need to send a PDF or email.

Q: What You Need to Do:

1. Log in to KSeF and check your inbox 2. Verify the data — whether the amount, NIP, and line items match 3. Accept the invoice (or reject it if there's an error) 4. Deduct VAT (if you're an active VAT taxpayer) That's it. No more sending photos of invoices to your accountant, no more losing PDFs. Everything is in KSeF. KSeF and the VAT Exemption Even if you use the subject-matter VAT exemption (turnover below 200,000 zł), KSeF applies to you. You issue invoices in the system, but without VAT rates — as exempt invoices (annotation "exempt from VAT" or rate "zw"). This is the most important change for small sole proprietorships (JDG): even those who have never been VAT payers must use KSeF. Penalties for Not Using KSeF During the first year (April 2026 – March 2027), penalties are deferred — the tax authority will not impose sanctions for failing to issue an invoice in KSeF. But the obligation itself applies from April 1, 2026. After the transitional period: Penalty for each invoice issued outside KSeF: up to 100% of the tax amount Penalty for failing to mark an invoice with a KSeF number: up to 100% of the tax amount KSeF and Your Accountant If you work with an accountant (like Oxyok), KSeF simplifies the collaboration: The accountant has access to your KSeF — they see invoices in real time You don't send photos of invoices by email — everything is in the system The standard audit file (JPK) generates automatically from KSeF Costs are deducted faster — supplier invoices are available immediately Frequently Asked Questions

The e-invoicing system (KSeF) from April 1, 2026 for all VAT taxpayers, including those who are exempt. How to issue, receive, and store e-invoices. A practical guide for sole proprietorships.

The e-invoicing system (KSeF) has been mandatory since April 1, 2026 for all VAT taxpayers — including those who use the VAT exemption. If you run a sole proprietorship (JDG), this system applies to you, regardless of whether you issue VAT invoices or exempt ones.

This guide explains what KSeF means in practice for a small business and how to prepare for it.

What Is KSeF?

KSeF is a Ministry of Finance platform where all invoices are issued, transmitted, and stored in structured form (XML FA(2)). You don't issue an invoice in your own software and send a PDF — the invoice is created inside the KSeF system.

What Does This Change in Practice?

You don't send PDFs — the contractor receives the invoice automatically in their KSeF system
The invoice has a KSeF-assigned number — not your own number
You deduct costs automatically — invoices from Polish suppliers appear in your KSeF on their own and are ready for VAT deduction
The standard audit file (JPK) generates itself — KSeF produces the JPK_V7 file from your invoices

Who Does KSeF Apply To?

From April 1, 2026:

All VAT taxpayers — active and exempt from VAT (if turnover is below 200,000 zł)
Sole proprietorships (JDG) on lump sum tax (ryczałt), tax scale (progressive), and flat tax 19% — if they are registered as VAT taxpayers or use the subject-matter exemption

Who Is Exempt from KSeF?

Individuals not conducting business activity (simplified invoices below 450 zł)
Certain taxpayers settling via lump sum tax (ryczałt) from seasonal activity (narrow exceptions)

How to Issue an Invoice in KSeF — Step by Step

Step 1: Log In to KSeF

Step 2: Choose Your Interaction Method

You have two options:

Interactively — fill out the form directly on the KSeF website (free, but time-consuming)
API / integration — your accounting software sends the invoice automatically (requires KSeF integration)

Step 3: Fill In Invoice Data

A structured invoice requires:

Seller and buyer data (NIP, name, address)
Issue date and date of sale
Line items (name, quantity, net price, VAT rate)
Total net, VAT, gross
Payment method and due date

Step 4: Receive Your KSeF Number

After sending the invoice, KSeF assigns it a unique number (the so-called KSeF number). This number must appear on every invoice — it's proof that it was issued correctly.

Step 5: The Contractor Receives the Invoice

Your contractor sees the invoice in their KSeF system automatically — you don't need to send a PDF or email.

How to Receive an Invoice from a Supplier in KSeF

Invoices from Polish suppliers arrive automatically in your KSeF. You don't need to request an invoice — it appears on its own.

What You Need to Do:

Log in to KSeF and check your inbox
Verify the data — whether the amount, NIP, and line items match
Accept the invoice (or reject it if there's an error)
Deduct VAT (if you're an active VAT taxpayer)

That's it. No more sending photos of invoices to your accountant, no more losing PDFs. Everything is in KSeF.

KSeF and the VAT Exemption

Even if you use the subject-matter VAT exemption (turnover below 200,000 zł), KSeF applies to you. You issue invoices in the system, but without VAT rates — as exempt invoices (annotation "exempt from VAT" or rate "zw").

This is the most important change for small sole proprietorships (JDG): even those who have never been VAT payers must use KSeF.

Penalties for Not Using KSeF

During the first year (April 2026 – March 2027), penalties are deferred — the tax authority will not impose sanctions for failing to issue an invoice in KSeF. But the obligation itself applies from April 1, 2026.

After the transitional period:

Penalty for each invoice issued outside KSeF: up to 100% of the tax amount
Penalty for failing to mark an invoice with a KSeF number: up to 100% of the tax amount

KSeF and Your Accountant

If you work with an accountant (like Oxyok), KSeF simplifies the collaboration:

The accountant has access to your KSeF — they see invoices in real time
You don't send photos of invoices by email — everything is in the system
The standard audit file (JPK) generates automatically from KSeF
Costs are deducted faster — supplier invoices are available immediately

Frequently Asked Questions

Do I need invoicing software?

No. You can issue invoices directly on the KSeF website (free). But accounting software with KSeF integration saves time.

Does KSeF apply to foreign invoices?

No. KSeF applies to domestic invoices (Polish NIP of seller and buyer). Foreign invoices (e.g., from Germany) are still issued the traditional way.

Does KSeF replace the standard audit file (JPK)?

Not directly, but KSeF generates data for JPK_V7 automatically. In practice, manually creating JPK_V7 from invoices is becoming a thing of the past.

What if I don't have internet access?

KSeF supports an offline mode — you can prepare an invoice in XML format and send it when you regain connectivity.

Need Help with KSeF?

I handle accounting for sole proprietorships (JDG) with full KSeF support — issuing, receiving, standard audit file (JPK). From 49 zł + VAT monthly.

Write to [email protected] or visit oxyok.com/pl.

Note: KSeF regulations are in a transitional period (April 2026 – March 2027). Penalties are deferred, but the obligation to issue invoices in the system applies from April 1, 2026. Consult an accountant.