KSeF

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  KSeF

  The KSeF invoice PDF and QR code: KOD I vs KOD II

  When an invoice is accepted, KSeF returns the UPO (official proof of receipt) and the KSeF number; the readable PDF is a visualisation Notaly generates from the FA(3) data, carrying the official KOD I QR. KOD I and KOD II are two different codes, not two states of one: KOD I is the verification link built by the issuer from the SHA-256 of the XML, and KOD II is the issuer's verification QR, signed with a KSeF certificate of type Offline, added only on an offline invoice.

  Tomek·Oct 12, 2026·3 min read

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  KSeF

  KSeF readiness checklist for small businesses

  Readiness for KSeF means having your party data, invoice fields, authentication method and a tested flow in place before your obligation applies. Work through a short checklist — buyer and seller NIPs, FA(3) field mapping, token authentication and a TEST run — so the switch is mechanical rather than a scramble.

  Tomek·Oct 12, 2026·3 min read

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  Integrations

  KSeF retries and idempotency: avoid duplicate invoices

  Retrying a timed-out KSeF submission blindly can create a duplicate invoice, because the request may have reached KSeF even though you never saw the response. The safe pattern is to attach a stable idempotency key on your side to every submission, check the invoice's status against KSeF before resubmitting, and only resubmit when you are certain no earlier attempt succeeded.

  Tomek·Oct 12, 2026·3 min read

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  KSeF

  KSeF sandbox testing: how to test without touching production

  You test KSeF integration in the TEST environment (api-test.ksef.mf.gov.pl), where every submission has no legal or tax effect. Notaly's sandbox sends to KSeF TEST with the platform's test credentials and gives you three free test invoices, so you can validate your FA(3) XML and the whole flow before going near production.

  Tomek·Oct 12, 2026·3 min read

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  KSeF

  How to check KSeF invoice status and retrieve the UPO

  When you create an invoice, the POST /invoices response returns submitted with a KSeF reference number, and the final decision — accepted or rejected — arrives later. You can verify it by polling GET /invoices/{id}, which re-checks KSeF while the invoice is still submitted, or by listening for the signed status webhook. The UPO and the KSeF number arrive together with the accepted status.

  Tomek·Oct 12, 2026·2 min read

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  KSeF

  KSeF TEST environment: how to test invoices before production

  The KSeF TEST environment (api-test.ksef.mf.gov.pl) is the Ministry of Finance's sandbox where you can send FA(3) invoices without touching production data. It uses the same FA(3) schema and the same status flow, so it is the safe place to validate your XML, your authentication and your status handling before going live. Notaly's sandbox maps to KSeF TEST and includes three free test invoices.

  Tomek·Oct 12, 2026·3 min read

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  KSeF

  KSeF token: what it is and how to generate one

  A KSeF token is the credential your system uses to authenticate to Poland's KSeF API and open an online session. You generate it in the KSeF portal (or via the API), provide it to your integration — or to Notaly in Connect KSeF — and it lets you submit invoices without a qualified seal. The token authenticates the session; it is not used to sign the invoice.

  Tomek·Oct 12, 2026·2 min read

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  KSeF

  KSeF token expiry and rotation: keep your integration alive

  A KSeF token is an authentication credential with a validity period, and when it expires your integration can no longer open sessions or submit invoices. The routine that keeps you running is simple: check the expiry date, generate a new token before the old one dies, and replace it in one place — Connect KSeF in Notaly.

  Tomek·Oct 12, 2026·3 min read

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  KSeF

  KSeF token vs certificate: two ways to authenticate

  KSeF accepts two ways to authenticate a session: a KSeF-issued token, or an XAdES signature made with a qualified signature or seal or a KSeF certificate. They are alternatives for the same step — proving who you are before you send an invoice — and in both cases the invoice XML itself is not signed: it is encrypted and sent in the online session. Notaly uses the token, so you do not need a qualified seal.

  Tomek·Oct 12, 2026·3 min read

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  KSeF

  KSeF UPO and invoice status: what happens after you send

  The UPO (Urzędowe Poświadczenie Odbioru) is the official proof of receipt that KSeF returns when it accepts a submitted FA(3) invoice. After you send an invoice it moves through a short status cycle — submitted, then accepted or rejected — and the UPO is the confirmation you archive as evidence. Reading that status correctly lets you automate retries and tell customers exactly where their invoice stands.

  Tomek·Oct 12, 2026·2 min read

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  KSeF

  VAT rates in KSeF: 23%, 8%, 5% and 0%

  The four VAT rates Notaly's e-invoicing API accepts are 23%, 8%, 5% and 0%, one rate per invoice line. The 7% rate, exemptions (zw) and reverse charge (odwrotne obciążenie, oo) are not supported today, so a line using one of them fails Notaly's validation with a 422 before it reaches KSeF.

  Tomek·Oct 12, 2026·3 min read

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  KSeF

  KSeF webhooks: automating invoice status end to end

  KSeF decides whether an invoice is accepted asynchronously, so the submit call alone is not the end of the story: Notaly polls KSeF for you and pushes the final result to your endpoint as a signed webhook — invoice.accepted (with the KSeF number and UPO), invoice.rejected, or invoice.error. Each webhook is signed with HMAC and retried with backoff, so you can build reliable order-to-invoice automation without polling yourself.

  Tomek·Oct 12, 2026·3 min read