KSeF Penalties Postponed to 2027: What Changed & Why

On September 16, 2026, Poland?s Ministry of Finance announced it will extend the penalty-free grace period for errors related to the National e-Invoice System (KSeF ? Krajowy System e-Faktur) until December 31, 2027. This gives businesses especially smaller ones joining the mandate in 2027 an extra year to refine processes without facing financial sanctions for operational mistakes.

The underlying obligation to use KSeF remains unchanged. Penalties are deferred; the system itself is not.

This update is particularly relevant for finance, AP/AR, and compliance teams at B2B companies preparing for (or already operating under) mandatory structured e-invoicing.

When Do KSeF Penalties Start?

Under the September 16, 2026, Ministry of Finance announcement, administrative penalties for KSeF-related errors are proposed to apply only from January 1, 2028 (i.e., after the extended grace period ends on December 31, 2027).

Previously, the soft-landing period was expected to end at the start of 2027. The extension responds to feedback from businesses, industry groups, tax advisers, and software providers during the phased rollout.

This is not yet law. It requires a legislative amendment. The Ministry has begun drafting the bill. Monitor the legislative process do not treat December 31, 2027, as final until the amendment is passed and published.

Is KSeF Mandatory in 2027?

Yes. From January 1, 2027, KSeF becomes mandatory for all remaining businesses once transitional periods for the smallest taxpayers expire on December 31, 2026.

Phased mandatory dates (issuance of structured e-invoices for domestic B2B):

Receiving invoices via KSeF has been required more broadly since the early waves. The penalty extension does not move any of these go-live dates.

Has the KSeF Penalty Deadline Been Extended? Is the Extension Law Yet?

Yes, the Ministry announced an extension of the penalty-free period to December 31, 2027.

No, it is not yet law. The Ministry of Finance has started work on the necessary draft legislation to allow time for the parliamentary process. Until the amendment is enacted and published, the extension remains a proposal. Plan accordingly but verify final wording once available.

What Happens If I Don?t Use KSeF?

The obligation to issue structured invoices through KSeF according to your category?s go-live date is unchanged. Issuing invoices outside KSeF without a statutory exception (e.g., specific offline or outage scenarios) remains non-compliant.

During the proposed grace period:

• Tax authorities (KAS) will prioritise support and reminders.
• They can still intervene in cases of invoices issued outside KSeF (except legally defined situations) and examine whether non-use leads to unreliable tax settlements.

Once penalties apply (proposed from 2028), administrative fines under Article 106ni of the VAT Act become available. Criminal fiscal liability for serious issues (defective, fictitious, or unreliable invoices) is a separate track and is not fully suspended by the administrative penalty deferral.

How Much Is the KSeF Penalty?

Once the penalty provisions take effect, under Article 106ni of Poland?s VAT Act the head of the tax office can impose an administrative fine by decision of:

• Up to 100% of the VAT amount shown on an invoice issued outside KSeF, or
• Up to 18.7% of the total invoice value where no VAT is shown (e.g., zero-rated or exempt transactions).

The fine is payable within 14 days of the decision being served. Amounts can be mitigated under general administrative procedure rules depending on circumstances, severity, and frequency, but they are not symbolic ? high-volume issuers face compounding risk from even low error rates.

Why This Matters for B2B Finance and Operations Teams

This is a runway, not a pause button. Most mid-size and large businesses have already been operating under KSeF for months. The extension primarily gives the final wave of smaller taxpayers and any teams still stabilising processes extra time to reduce error rates without financial exposure.

Key distinctions to keep clear:

• Obligation vs. penalties ? You must still use KSeF on schedule. The relief covers errors in how you use it, not a decision to bypass it.
• Support vs. enforcement ? KAS intends to prioritise education and assistance in 2027 but can still act on non-compliant issuance and unreliable settlements.
• Legislative status ? Treat the December 31, 2027, date as planned until the amendment is law.

What Businesses Should Do Now

1. Keep KSeF integration and process work on schedule ? use the extra time for testing, edge cases (offline mode, FA (3) schema, authentication), and staff training rather than delaying go-live.
2. Audit current issuance: identify any volume still happening outside KSeF without a documented statutory exception.
3. Train AP/AR and finance teams on structured invoicing rules, offline/outage procedures, and common error sources.
4. Track the draft law closely so you know exactly when (and how) the extended protection is finalised.
5. Do not confuse penalty relief with deadline relief ? your mandatory date (February 2026, April 2026, or January 2027) has not moved.

Frequently Asked Questions

Is KSeF still mandatory if penalties are postponed?
Yes. The proposed protection concerns mistakes made when operating KSeF and does not make the system optional. Businesses still must use KSeF for domestic B2B invoicing according to their applicable go-live date.

When do KSeF penalties start now?
Under the September 16, 2026, announcement, penalties would not apply until January 1, 2028, provided the Ministry's draft law is passed. Until then, the extension is a proposal, not confirmed law.

Is the KSeF penalty extension confirmed law yet?
No. It requires a legislative amendment. The Ministry of Finance has only begun drafting the bill as of the announcement date.

How big are KSeF penalties once they apply?
Up to 100% of the VAT shown on an invoice issued outside KSeF, or up to 18.7% of the total invoice value where no VAT is shown, under Article 106ni of the VAT Act.

Who benefits most from this extension?
Smaller businesses and the newest group of taxpayers, those whose transitional periods end December 31, 2026, and for whom KSeF becomes mandatory January 1, 2027.