From 1 April 2026, companies are required to use Poland’s National e-Invoicing System (KSeF).
Based on survey by SaldeoSMART, the first weeks of mandatory use for large companies have already shown where implementations tend to fail—not because of the obligation itself, but because of gaps in process readiness, access management and day-to-day document handling. Poor preparation can lead to rejected invoices, delays in bookkeeping and increased compliance risk.
In practice, challenges usually stem from insufficient preparation of the surrounding processes. KSeF often highlights informal workarounds that previously went unnoticed.
Below we outline three common KSeF implementation mistakes and how SMEs can avoid them ahead of the April 2026 deadline.
3 common KSeF implementation mistakes
1) Permissions and certificates are not set up properly
Companies often generate certificates but do not set up user permissions correctly. As a result, access exists technically, but authorised staff cannot issue, receive or download invoices in KSeF.
- Remember: certificates do not replace permissions—assigning the correct KSeF roles is required to issue and retrieve invoices.
- Select the right certificate model: for teamwork, company-level access (NIP-based) is typically easier to manage; PESEL-linked certificates are individual and should not be shared.
2) No clear arrangements with the accounting office
Many businesses do not agree with their accounting office how KSeF work should be split. Assuming that “the accountant will handle everything” can create delays and errors—especially when roles are unclear.
- Who grants and maintains KSeF permissions and certificates
- Who downloads incoming invoices and how frequently
- Who monitors invoice statuses (accepted/rejected) and corrects issues
- Who provides operational support when the system is unavailable or errors occur
3) Underestimating the scale of change
KSeF is not only an IT project. It affects the full invoice lifecycle—issuance, receipt, approval, circulation, archiving and access to data across the organisation. Companies have faced several issues:
- changing internal processes is one of the main barriers to KSeF implementation.
- adapting systems and software to the new requirements as a key challenge.
- Mapping or re-mapping the invoice workflow end-to-end (sales, procurement, approvals and accounting).
- Update internal procedures and train users involved in issuing and accepting invoices.
- Confirm ERP/accounting system readiness and test KSeF integration in advance.
Free Ministry of Finance tools: when they are enough, and when they are not
The Ministry of Finance provides free manual tools for using KSeF and these tools may be sufficient for very small operations, but limitations typically appear when invoice volumes increase or when several people participate in invoice handling.
Free manual tools may be enough if:
- you issue a very low number of invoices per month,
- a single person handles invoicing and document flow,
- you do not need integration with an ERP/accounting system.
You may need an integrated solution if:
- you process many invoices or multiple document types,
- several employees need access and approval rights,
- you require automated circulation, controls and archiving,
- your accounting is handled externally and you need clear, auditable hand-offs.
What to do now: review roles and authorizations, confirm how invoices will circulate and be approved, and test your tools (including integration, if applicable) before the obligation becomes effective for your business.
If you would like support assessing readiness or selecting an approach suitable for your organisation, Leinonen Poland can assist you with the implementation and align responsibilities between your team and your accounting function.
Consequences of poor KSeF preparation
- invoice issuance or receipt disruptions due to missing permissions or incorrect setup
- rejected invoices and additional workload to correct and resend documents
- delays in bookkeeping and reporting caused by incomplete document flow
- higher risk of errors and increased scrutiny during tax audits
How Leinonen Poland can help
Leinonen Poland supports businesses operating in Poland with practical KSeF readiness work, combining process design, system setup and day-to-day compliance support:
- KSeF implementation assistance and testing
- support with permissions, authorisations and operational setup
- workflow design for invoice circulation, approvals and archiving
- ongoing accounting and tax compliance support in Poland
If you want to reduce KSeF risks and ensure a smooth transition, our tax and accounting specialists are ready to support you.
