KSeF - What It Is and How to Prepare Your Business for Mandatory E-Invoicing in Poland Starting 2026

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KSeF**, short for Krajowy System e-Faktur (National e-Invoicing System), is one of the hottest topics in Poland’s business and tax landscape. Beginning January 1, 2026, using KSeF will become mandatory for all companies operating in Poland - from freelancers and sole proprietors to large corporations.

In this article, we’ll break down:

• what KSeF actually is,

• why it was introduced,

• what consequences it brings for companies,

• how e-invoicing will work in practice,

• and how Flowtly makes compliance simple with full KSeF integration.

What is KSeF?

KSeF (Krajowy System e-Faktur) is a government-run digital platform that enables:

• issuing invoices in a structured XML format,

• sending invoices directly to business partners,

• storing documents within the system for 10 years,

• automatically reporting invoice data to the Polish tax authorities.

A “structured invoice” is simply an electronic invoice formatted according to a national XML schema. This allows accounting systems to read and process invoice data automatically, without manual data entry.

Why Was KSeF Introduced?

The Polish Ministry of Finance is rolling out KSeF to:

• close the VAT gap and reduce tax fraud,

• simplify tax reporting and compliance,

• eliminate the need for JPK_FA (Polish VAT invoice reporting),

• speed up VAT refunds (down to 40 days instead of 60),

• increase transparency and security in invoice circulation.

Who Will Be Affected by KSeF?

Starting in 2026, KSeF will be mandatory for all businesses issuing invoices in Poland:

• freelancers and sole proprietors (JDG),

• small and medium-sized businesses,

• large corporations,

• foreign entities issuing invoices in Poland.

There will be no exceptions – every invoice must go through the system to be legally valid.

Consequences for Businesses

The shift to mandatory e-invoicing means major organizational and technological changes:

1. New invoice format - invoices will no longer be PDFs sent by email; they must be issued in XML.
2. System integration required - your invoicing or ERP software must be adapted to connect with KSeF.
3. New accounting workflows - document circulation and bookkeeping procedures will need updating.
4. Penalties for non-compliance - issuing invoices outside of KSeF may result in fines or invoices being invalid.

How to Prepare Your Business for KSeF

• Audit your current invoicing system - does it support XML and connect to KSeF?

• Train your team - accounting, finance, and sales staff must understand the new process.

• Start testing early - don’t wait until 2026; pilot the new workflow in 2025 to avoid disruptions.

Flowtly – Full Integration with KSeF

At Flowtly, we focus on simplicity and automation. That’s why our platform will be fully integrated with the National e-Invoicing System (KSeF).

With Flowtly, you’ll be able to:

• issue and receive invoices directly within the system,

• ensure 100% compliance with Polish Ministry of Finance requirements,

• manage all documents in one place alongside your other business processes,

• avoid the hassle of juggling multiple tools.

💡 With Flowtly, your transition to mandatory e-invoicing will be smooth and stress-free.

Final Thoughts

Mandatory e-invoicing via KSeF in 2026 is both a challenge for Polish businesses and an opportunity to simplify workflows and enhance financial transparency.

👉 With Flowtly, you can rest assured - our platform will be fully compliant with KSeF, making the shift to e-invoicing seamless.