Help & getting started

A. Install

1. Install the KSeF Connect app on your Stripe account (from the Marketplace or from an install link you received).
2. After install, Stripe opens the app's settings screen. You can also find the app under the Apps menu in the Stripe Dashboard.

B. Get a KSeF credential

You need one of two ways to authenticate with KSeF. We recommend a certificate — tokens stop working at the end of 2026.

Option 1 (recommended): KSeF certificate

1. Sign in to the Ministry of Finance's KSeF application (production: ksef.podatki.gov.pl; for testing use the demo environment).
2. Generate a certificate for your entity. You'll receive a certificate file (.crt or .pem), a private key file (.key), and a password protecting the key.
3. Keep all three — you'll need them in step C.

Option 2: authorization token

1. In the KSeF taxpayer application, generate an authorization token for your NIP.
2. Copy the token — you'll paste it into the app settings (step C).

C. Configure in the app (Stripe → Settings)

1. Choose the KSeF environment — Test (demo) for trials, or Production for real invoices.
2. Choose the authentication method — Certificate (recommended) or Token.
3. For a certificate, click "Open upload window". A separate tab opens on our server (Stripe can't accept these file types inside the app window). Upload the certificate file (.crt/.pem), the key file (.key), enter the password, and submit. The settings view refreshes automatically once the upload completes.
4. Fill in seller details — enter your NIP and click "Fetch from CEIDG" to auto-fill the name and address (for sole proprietors). Companies fill this in manually.
5. Set the submission trigger — on finalization, on payment, or manual — and choose whether to write the KSeF reference into the Stripe invoice metadata.
6. Click "Test connection" to confirm your credentials work.

D. Day-to-day use

1. Once configured, invoices are submitted to KSeF according to your chosen trigger.
2. The app home page shows counts by status and a list of invoices needing attention, with the option to retry failed submissions.
3. For each invoice you can download the UPO (KSeF confirmation) and the generated FA(3) XML file.

E. Troubleshooting

1. Invoice "skipped": most often a missing buyer NIP (a B2C invoice). KSeF only handles B2B invoices.
2. Authentication / certificate error: check that you uploaded the correct certificate and key with the right password, and that the selected environment (Test/Production) matches the certificate.
3. Incorrect seller details: fill in the NIP and address; companies should enter the data manually.
4. Switching environments: after switching between Test and Production, run "Test connection" again.

Contact

Need help? Email support@ksef-connect.pl.