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KSeF in Poland
KSeF guidance for companies operating in Poland, written for English-speaking group finance, compliance and engineering teams.
Designing a reliable KSeF API integration: sessions, certificates and the failure modes that matter
KSeF API 2.0 has applied since 1 February 2026; API 1.0 closed between 26 and 31 January 2026. Encryption is mandatory in batch and interactive modes.
The KSeF audit trail: documenting every automated operation, and what the system does not keep for you
KSeF keeps the accepted invoice and its numer KSeF. It keeps nothing about your failed attempts, your offline24 decisions or your approvals — those are yours.
What KSeF automation actually costs: cost per invoice, cost per API call, and how a group controls both
KSeF carries no fee to the Polish administration: cost comes from software, integration and API operations. How to compute cost per invoice and per call.
Automating invoicing into KSeF: the four levels, and the controls that belong in front of each
Receiving structured invoices became mandatory on 1 February 2026, issuing on 1 April 2026. Automate receipt first — an accepted invoice cannot be deleted.
Duplicates and retries in KSeF: why an invoice submitted twice is a tax problem, not a data problem
A KSeF timeout is not a rejection: the invoice may already hold a numer KSeF. Resend it and the second invoice cannot be deleted, only corrected.
Approval thresholds before a KSeF invoice becomes irreversible
An invoice accepted by KSeF receives a numer KSeF and can be corrected but never deleted, so approval controls must run before submission, not after it.
offline24, awaria and niedostępność: three KSeF offline states, three different obligations
KSeF has four offline states: offline24 and niedostępność transmit by the next working day, awaria allows 7 working days, total failure none at all.
KSeF penalties from 1 January 2027: the exposure, and how a group documents an automated process
From 1 January 2027 an invoice issued outside KSeF carries a penalty of up to 100% of the tax shown, or 18.7% of the gross total where no tax is shown.

In practice

The control has to run before the invoice becomes irreversible.

An accepted structured invoice can be corrected but never deleted, and from the penalty date every defect has a price. Barzel puts the approval threshold, the duplicate check and the signed record in front of submission, so the process can be defended on the day an auditor or the tax authority asks.

95 days leftKSeF penalties apply from 1 January 2027

BarzelVault

The AI action firewall: decide what an agent may do before it does it.

Approval thresholds and policy checks enforced before execution; human approvals that expire and escalate.
Cryptographically signed audit receipts: trigger, inputs, policy version, approver, outcome.
Credential isolation, spend and action limits, and an emergency kill switch.

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BarzelOps

Governed workflow automation across the systems that run the business.

Durable, idempotent execution: a timeout is retried once, never filed twice.
Human approval checkpoints that pause the workflow and resume it.
Isolation per entity or client, signed evidence receipts and a portable manifest; HubSpot, Xero, Gmail, Google Drive and Slack.

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Poland

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The control has to run before the invoice becomes irreversible.

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