Poland’s KSeF in 2026: offline24, permissions and safe integration

01

Facts: who uses KSeF in the second half of 2026?

Mandatory KSeF invoicing has been phased in. It applied from 1 February 2026 to businesses whose gross sales exceeded PLN 200 million in 2024, and from 1 April 2026 to remaining businesses and other invoice issuers, subject to statutory exceptions. Businesses have been required to receive invoices through KSeF since 1 February 2026.

A transitional rule applies to the smallest taxpayers until the end of 2026. If monthly gross sales documented by invoices within KSeF scope do not exceed PLN 10,000, mandatory issuance in the system has not yet started. Once the threshold is exceeded, the obligation begins with the invoice that crosses it and, according to Ministry guidance, the taxpayer does not return to the earlier rules in later months.

Mandatory KSeF does not cover B2C invoices. The information in this article was checked on 24 September 2026 and is general operational guidance, not individual legal or tax advice. Confirm borderline cases with your accounting or tax adviser.

02

Facts: system scale and the transitional period

On 30 March 2026, the Ministry of Finance reported that KSeF had accepted more than 87 million invoices in its first two months and that over 345,000 entities had issued documents. More than 3 million invoices were submitted on 3 March alone. KSeF is therefore operational invoicing infrastructure, not merely an implementation project.

The Ministry describes 2026 as a transitional year in which penalties are not imposed for errors related to the use of KSeF. This does not remove the need to control accounting, duplicates, dates, permissions and transmission deadlines. A process failure can still delay payment, interrupt posting or require a correction.

03

Facts: online, offline24, unavailability and KSeF failure

In online mode, the invoice file is sent to KSeF in real time. Every taxpayer may use offline24: the invoice is created electronically using the FA(3) structure and sent to KSeF without undue delay, no later than the next business day after issuance.

When KSeF has announced unavailability, the invoice is sent no later than the day after that unavailability ends. Following an officially announced KSeF failure, the period is seven business days after the failure ends. During a total failure announced through mass media, invoices are not subsequently submitted to KSeF.

• online: submission and processing in the current session;
• offline24: submission no later than the next business day;
• KSeF unavailability: submission no later than the day after it ends;
• KSeF failure: submission within seven business days after it ends;
• total failure: the document remains outside KSeF and is not submitted later.

04

Facts: permissions, certificates and invoice receipt

A type 1 KSeF certificate is used for authentication. A type 2 certificate is required for the QR code that confirms the issuer’s identity in special modes. Official guidance states that a certificate is valid for no more than two years. A company without a qualified electronic seal may need ZAW-FA to appoint a person acting on its behalf, while a sole trader generally receives the owner permission automatically.

A Polish VAT taxpayer receives an invoice issued in offline24 through KSeF. For entities identified in the legislation, including consumers and foreign counterparties, the invoice may be provided outside the system in an agreed form with the required QR codes. The process for issuing a visualisation or PDF should therefore account for the buyer type and the document’s processing status.

05

WEBee recommendation: design two complete workflows

Implementation does not end with submitting a sales invoice. A business needs separate but connected outbound and inbound processes. Each should have an owner, a measurable handling time, change history and a clear point at which a person takes over an exception.

For sales, trace the path from source data through FA(3) validation, submission, status and KSeF number to accounting and customer information. For purchases, retrieve invoices regularly, identify the supplier and order, detect duplicates, route the document for approval and pass it to payment.

• outbound: source → validation → KSeF → status → number and acknowledgement → posting;
• inbound: retrieval → identification → duplicate control → approval → payment;
• exception: error message → owner → correction or retry → confirmation;
• continuity: mode change → offline queue → submission deadline → record reconciliation.

06

WEBee recommendation: controls for ERP or accounting integration

The integration should recognise whether an operation has already succeeded and retry only unfinished work safely. The ERP invoice number, technical submission identifier, KSeF number and official acknowledgement must be linked. A message saying only “sent” is not sufficient confirmation.

Permissions and certificates need an owner, expiry date, deputy and prompt revocation after a role change. Monitoring should identify rejected documents, long-running jobs, items left in the offline queue and purchase invoices that have not moved to further processing.

• protection against duplicate submission and duplicate posting;
• controlled retries with a limit and a dead-letter queue;
• alerts for a missing KSeF number, acknowledgement or missed deadline;
• a register of permissions, certificates and renewal dates;
• document-count reconciliation between KSeF, ERP and accounting;
• an audit-ready log of decisions and actions.

07

WEBee recommendation: a ten-day readiness review

Start by collecting the tools, roles, certificates and invoice volumes in use. Then follow one real sales invoice and one purchase invoice from start to finish. Finally, run an unavailability exercise: stop the test connection, activate the offline queue, verify alerts and perform a controlled submission.

The output should be a short gap register with owners and dates, not a general statement that “KSeF works”. Prioritise issues that can stop invoicing, payment, document access or the timely return from a special mode to normal operations.

• days 1–2: scope, volumes, systems and owners;
• days 3–4: permissions, certificates, deputies and expiry dates;
• days 5–6: end-to-end sales and purchase invoice paths;
• days 7–8: errors, duplicates, retries and status reconciliation;
• day 9: an offline24 or unavailability test in a test environment;
• day 10: gaps, priorities, owners and remediation plan.