Frequently Asked Questions

What is KSeF Connect?

It's a Stripe App that automatically converts invoices issued in Stripe into the structured FA(3) format and submits them to Poland's National e-Invoicing System (KSeF). After a successful submission it writes the KSeF reference number back to the Stripe invoice.

Who is it for?

Polish businesses (sole proprietors and companies) that bill through Stripe and want to send invoices to KSeF without manual export or re-keying.

What do I need to get started?

A Stripe account, a KSeF credential (KSeF certificate or authorization token), and your seller details (NIP and address). We walk through it step by step in Help.

Certificate or token — which should I use?

We recommend a KSeF certificate. Authorization tokens are a transitional solution and stop working at the end of 2026 — certificates are required from 2027. The App supports both methods.

How do I get a KSeF certificate?

You generate it in the Ministry of Finance's KSeF taxpayer application. You'll receive a certificate file (.crt), a private key file (.key), and a password. Detailed instructions are in Help.

When are invoices sent to KSeF?

You choose when: on invoice finalization, on payment, or manually only. You can change this in the app panel in Stripe.

What about invoices without a buyer NIP (B2C)?

KSeF handles B2B invoices and requires the buyer's NIP. Invoices without a buyer NIP are automatically skipped (marked "skipped").

How do corrections work?

When you issue a credit note in Stripe, the App prepares an FA-KOR correction invoice referencing the original KSeF number and submits it.

Can I test before going live?

Yes. The App supports the KSeF test environment (demo). Invoices submitted in the test environment or in Stripe test mode are not counted toward billing.

How much does it cost?

Billing is based on the number of invoices submitted in a given month (volume-tiered pricing). Current tiers and prices are shown during installation and in the Stripe billing panel. Prices are subject to VAT.

Is my certificate safe?

Yes. The certificate, private key, password and tokens are stored encrypted only. The private key is used solely server-side to sign the KSeF authentication request and is never disclosed. Connections are encrypted (HTTPS).

What Stripe data does the app access?

Only what's necessary: read invoices, write the KSeF reference to the invoice, read buyer data (for the Podmiot2 section), and read credit notes. Details are in the Privacy Policy.

What is UPO?

UPO (Urzędowe Poświadczenie Odbioru) is the official confirmation that KSeF received your invoice. The App stores it and lets you download it.

How do I uninstall and delete my data?

Uninstall the App from the Stripe panel. On uninstall, access tokens are deleted and the account is deactivated. To erase remaining data, email support@ksef-connect.pl.

Where can I get help?

Email support@ksef-connect.pl — we'll help with setup and any submission errors.