Your First KSeF E-Invoice: A 10-Point Checklist

Sending your first invoice in KSeF looks like a single click. The catch is that half of what determines success happens before you ever open the form: whether your login works, whether your software generates the right schema, whether your buyer's tax ID is correct.

The obligation is already live. Large companies have issued through KSeF since 1 February 2026, all other businesses since 1 April 2026, and the smallest taxpayers (monthly sales up to PLN 10,000 gross) join on 1 January 2027. Under the current act, penalties under Article 106ni of the VAT Act apply from 1 January 2027. On 16 September 2026 the Ministry of Finance announced it will move them to 1 January 2028; that is a bill not yet passed, and it moves only the penalties, not the obligation to use KSeF. It is a calm moment to walk through your first invoice. Here are ten concrete things to tick off.

Before you click: does the obligation apply to you yet?

1. Confirm when you must issue through KSeF. The rollout is phased: companies with 2024 turnover above PLN 200 million started on 1 February 2026, all remaining businesses on 1 April 2026, and the smallest taxpayers (monthly sales up to PLN 10,000 gross) on 1 January 2027. Note that receiving invoices via KSeF applies to every business from 1 February 2026, regardless of size. The current schedule lives at ksef.podatki.gov.pl (legal basis: the Act of 5 August 2025, Journal of Laws — Dz.U. 2025 item 1203).

Your identity in the system

2. Verify your tax ID (NIP) and company data. In the FA(3) schema, the NIP (Polish tax identification number) in the Podmiot1 (seller) element is the authorization key — without it the invoice will not issue at all. Before you send anything, check that your legal name, address and especially your NIP are correct and current. A typo in the NIP isn't cosmetic; it stops the transmission.

3. Choose your authentication method. If you run a JDG (sole proprietorship) and work manually, Profil Zaufany (Trusted Profile, a free government e-ID), the mObywatel app, mojeID (online banking) or an e-ID card is enough (since 14 February 2026 via login.gov.pl). If you issue from software, run a company, or act as an accounting office, you'll need a qualified seal/signature or a dedicated KSeF certificate. Tokens also exist: under the current rules KSeF tokens expire on 31 December 2026. At consultations on 9 June 2026 the Ministry of Finance proposed keeping them, but no regulation has been adopted yet, so moving to a KSeF certificate is the safer choice. Biurko does not connect with a token. In Biurko you authenticate with a certificate or Profil Zaufany (step-by-step guide). For steady, automatic work, order a KSeF certificate in Biurko — after the first connection with Profil Zaufany — and use it to connect.

4. Grant permissions. As a JDG owner you hold owner permissions automatically once you log in with your own number. A company must first designate an authorized person. The key point: your accounting office and employees can only act on permissions you grant them inside KSeF — without that, your software cannot send invoices on your behalf. This step is the single most common blocker for businesses with outsourced bookkeeping.

The technical minimum

5. Make sure your software issues in the FA(3) schema. Since 1 February 2026, FA(3) is the only valid structured-invoice template — files generated in the older FA(2) version are simply rejected. If you're on existing software, ask your vendor directly whether they've shipped FA(3), not whether they're "working on it."

6. Verify your buyer's data (their NIP). The Podmiot2 (buyer) element requires a correct buyer tax ID. A wrong number means the invoice lands with the wrong entity — or doesn't issue at all. Check the NIP against the GUS (statistical office) registry and the official VAT "white list" before you hit send. KSeF doesn't offer the easy "send now, fix later" you had with a PDF.

How sending actually works

7. Understand when an invoice is "issued" and what the KSeF number is. In online mode, the issue date is the day the invoice reaches KSeF — not the date written on the document. The system assigns each accepted invoice a 35-character KSeF number; in online mode, together with the UPO, it confirms that the document was accepted. An invoice rejected by KSeF has not been issued, while in the offline modes an invoice legally exists even before it gets a number. Once accepted, you download the UPO (Urzędowe Poświadczenie Odbioru, the official acceptance receipt).

8. Have a plan for downtime — offline24 mode. When KSeF doesn't respond, don't get stuck. In offline24 mode you issue the invoice outside the system (with an offline code and QR), and send it to KSeF no later than the next business day — the issue date then stays the date in field P_1. For an officially declared Ministry outage, a separate emergency mode gives a longer window to upload — 7 business days from the end of the outage announced by the Ministry. Check whether your software handles this automatically — Biurko switches to offline24 and tracks the upload deadline for you (more on offline24).

What you don't send — and the PLN 10,000 trap

9. Know what stays outside KSeF — and don't mistake a buffer for an exemption. B2C sales (to consumers) are not covered by the KSeF obligation — you can still issue them in KSeF voluntarily; cash-register receipts, pro forma invoices and credit notes stay outside KSeF. The most common misunderstanding is the PLN 10,000 limit: it is not a micro-business exemption, but a conditional buffer. Until 31 December 2026, taxpayers whose monthly gross value of B2B invoices covered by the KSeF obligation does not exceed PLN 10,000 may issue outside KSeF. Invoices to consumers, receipts with a NIP, simplified invoices up to PLN 450 and cash-register sales do not count toward the limit. Exceeding the limit is irreversible: from the invoice that crossed it, you issue in KSeF — with no grace period and no "from next month."

The last step before going live

10. Issue a test invoice in the demo environment. To practise without legal effect, use the Biurko demo (demo.biurko.io, 7-day access, the KSeF demo environment). An account on app.biurko.io sends invoices to production KSeF, so every invoice you send there is real. On the demo you'll see the full flow dry-run: schema validation, KSeF-number assignment and UPO retrieval. The KSeF 2.0 Taxpayer Application provides separate test and demo environments that remain available even after production launch — use them so your first real invoice isn't also your first test.

The checklist (tick it off)

• I know when I'm obliged to issue through KSeF (1 Feb / 1 Apr 2026 / 1 Jan 2027)

• My company's NIP and data are correct and current

• I have a working login method (Profil Zaufany or a certificate)

• I've granted permissions to my accounting office and employees

• My software issues invoices in the FA(3) schema

• I verify the buyer's NIP (GUS / white list) before sending

• I know what the 35-character KSeF number and the UPO are

• I have a plan for offline24 mode and system downtime

• I know what does NOT go to KSeF and how to count the PLN 10,000 limit

• I've sent a test invoice in the demo environment

Wrapping up

Your first e-invoice isn't hard — it's just different from a PDF. Most launch-day problems aren't "KSeF is down"; they're a missing login, missing permissions, or software stuck on the FA(2) schema. Tick off these ten items and sending becomes a formality. You have time to do it calmly: under the current act, penalties under Article 106ni of the VAT Act apply from 1 January 2027, and the Ministry of Finance has announced it will move them to 1 January 2028 (a bill not yet passed).

Biurko walks you through the whole process from the start: certificate authentication, issuing in FA(3), automatic offline24 mode, UPO and contractor verification in one place. Create an account — every new company gets 14 days of the TEAM plan with no card, then moves to the free FREE plan — and send your first e-invoice without the stress.

FAQ

When do I have to start issuing invoices in KSeF? It depends on company size: large entities (2024 turnover above PLN 200 million) from 1 February 2026, all other businesses from 1 April 2026, and the smallest (monthly sales up to PLN 10,000 gross) from 1 January 2027. Receiving invoices via KSeF has applied to everyone since 1 February 2026.

Do I need a certificate for KSeF, or is Profil Zaufany enough? For manual work as a sole proprietor, Profil Zaufany, the mObywatel app, mojeID (online banking) or an e-ID card (since 14 February 2026 via login.gov.pl) is enough. If you issue from software, run a company, or act as an accounting office, you need a KSeF certificate or a qualified seal/signature, because those enable automatic sending and the granting of permissions.

What do I do if KSeF is down when I need to issue an invoice? You issue the invoice in offline24 mode — outside the system, with an offline code and QR — then send it to KSeF no later than the next business day. The issue date stays the date in field P_1. Good software (such as Biurko) switches to this mode automatically and tracks the upload deadline.

What is the KSeF number, and is an invoice valid without it? The KSeF number is a 35-character identifier the system assigns to every accepted invoice. In online mode the number and the UPO confirm that the document was accepted; an invoice rejected by KSeF has not been issued, while in the offline modes an invoice legally exists even before it gets a number.

Does the PLN 10,000 limit exempt a small business from KSeF? No. It's not an exemption but a conditional buffer during the transition period. The limit covers the monthly gross value of B2B invoices subject to the KSeF obligation (invoices to consumers, receipts with a NIP, simplified invoices up to PLN 450 and cash-register sales do not count). From the invoice that crosses it you must issue in KSeF — immediately, with no grace period, and exceeding it is irreversible.