How to Install the S2K Application on Your Stripe Account

Clicking the installation link takes us to the Stripe Apps installation page where we can select the account on which we'll install S2K and review the permissions we're granting to the application. After clicking "Install," the application installation process will begin.


After installation is complete, we land on a page confirming the S2K installation. From here, we can return to our application settings in Stripe, where we should fill in the missing information about our company.

The application reads some information from our Stripe account, while the rest we need to fill in ourselves. This includes information required for proper invoice submission to KSeF, including taxpayer status or VAT exemption information and its legal basis.

After completing the data, we click "Save changes," and if all required information is filled in, a KSeF settings section appears below the form.

To authorize S2K in KSeF, we click "Connect to KSeF" and then the generated link, which will take us to the authorization page.

KSeF authorization involves downloading a prepared XML file, signing it with a trusted profile, and then uploading the signed file back to S2K. KSeF verifies whether the signature author has permissions for the KSeF account for the given tax ID number. If so, our application generates the necessary certificates that will be used for automatic invoice submission.

After uploading the signed XML file, we receive information that the authorization status is being verified. This may take from several to even several dozen seconds if traffic on KSeF servers is high. If we don't want to wait, we can return to Stripe - we'll be able to check the result on the application settings page. However, if we wait, a few moments later a screen confirming successful authentication should appear.

When we return to the application settings page in Stripe, another option will appear in the KSeF settings section - we can select the mode in which the application will operate. Invoices can be sent automatically after they are finalized in Stripe, which will certainly be appreciated by entrepreneurs running subscription or e-commerce sales. For those who issue invoices manually or want full control over what is sent to KSeF, there is also an option for manual invoice submission.

In the next tutorial, we'll describe how invoice data from Stripe is mapped to the format required for KSeF, and what the submission process itself looks like.