The introduction of mandatory e-invoicing via the National e-Invoice System (KSeF) has significantly changed not only how invoices are issued, but also how VAT is reported.
As of 1 February 2026, taxpayers are required to apply new versions of the JPK_VAT structure with declaration, fully aligned with KSeF reporting rules.

These changes affect both sales and purchase records and require adjustments not only in accounting systems, but also in internal VAT reporting procedures.

New JPK_V7 structure effective from February 2026

Starting with the VAT settlement period for February 2026, taxpayers must use the following structures:

• JPK_V7M(3) – for monthly VAT taxpayers
• JPK_V7K(3) – for quarterly VAT taxpayers

The updated structures were published in December 2025 and are the only valid VAT reporting formats from that point onward. Previous versions of JPK_VAT will no longer be accepted.

KSeF number as a mandatory reporting element in JPK_VAT

One of the most important changes introduced by the new JPK_VAT structure is the obligation to report the KSeF identification number for invoices covered by the system.

What is the KSeF number and where is it reported?

The KSeF number is assigned once an invoice is successfully submitted to the system and confirmed by an official receipt (UPO). Under the new rules, the KSeF number:

• is reported both in sales and purchase VAT records,
• is not part of the invoice XML file,
• is included in a separate field in the JPK_VAT record,
• consists of 32 characters,
• must not be confused with the UPO reference number.

The internal invoice number assigned by the taxpayer under their own numbering system remains mandatory and is reported independently of the KSeF number.

Common reporting mistakes

In practice, taxpayers often confuse:

• the internal invoice number,
• the KSeF number,
• the UPO reference number.

Only the KSeF number should be reported in the relevant JPK_VAT field.

Missing KSeF number in JPK_VAT – applicable invoice markers

If the KSeF number is not available at the time of filing JPK_VAT, taxpayers must apply one of the additional reporting markers introduced in the new structure.

OFF – invoices issued during KSeF unavailability

The OFF marker applies to invoices issued:

• during KSeF outages,
• in cases of temporary system unavailability,
• when technical issues prevent issuing a structured invoice.

If the invoice is later submitted to KSeF before filing JPK_VAT, the KSeF number should be reported instead of the OFF marker.

BFK – invoices issued outside KSeF

The BFK marker applies to invoices issued outside KSeF where there is no obligation to use the system, including:

• B2C transactions,
• invoices issued to non-VAT taxpayers.

Both electronic and paper invoices may fall under this category.

DI – documents without a KSeF number or offline24 invoices

The DI marker applies to:

• documents other than invoices,
• invoices issued in offline24 mode,
• invoices that do not yet have a KSeF number at the time of filing JPK_VAT.

Such transactions must be reported as taxable sales and marked as DI in the VAT records.

JPK_VAT correction after receiving the KSeF number

If a document was initially reported with the DI marker and the KSeF number is obtained later, the taxpayer is required to:

• submit a corrected JPK_VAT file,
• supplement the missing KSeF number,
• remove the DI marker.

Failure to correct the JPK_VAT may be treated as a VAT reporting error.

Combining invoice markers in the new JPK_VAT structure

The updated JPK_VAT structure allows certain markers to be used simultaneously.

Permitted marker combinations

The DI marker may coexist with:

• RO or WEW on the sales side,
• VAT_RR or WEW on the purchase side.

Other existing markers (RO, WEW, FP, VAT_RR, MK) continue to apply under the current rules.

Notably, the FP marker will remain applicable until the end of 2026 for both structured invoices and invoices issued via cash registers, even though not all such invoices must be issued through KSeF.

How to prepare for JPK_VAT and KSeF reporting in 2026

The new JPK_V7(3) structure requires more than a technical system update. Taxpayers should also:

• review internal invoice circulation procedures,
• define rules for assigning and tracking KSeF numbers,
• ensure timely submission of invoices to KSeF,
• prepare clear procedures for JPK_VAT corrections.

Lack of consistency between accounting systems and KSeF processes significantly increases VAT compliance risk.

Final remarks

The JPK_V7(3) structure introduces more detailed VAT reporting and higher compliance requirements. Mandatory KSeF numbers and new markers such as OFF, BFK and DI make VAT reporting more process-driven than ever before.

Early system adjustments and procedural preparation will be essential to ensure smooth and compliant VAT reporting starting with the February 2026 settlement period.