How to Connect Stripe with KSeF - A Practical Guide for Entrepreneurs
26 stycznia 2026
From February 2026, large companies with revenues exceeding 200 million PLN must issue invoices through KSeF, and from April 2026 the obligation will cover all other entrepreneurs. If you accept payments through Stripe, a problem arises – Stripe does not connect directly with the Polish e-invoicing system.
Why doesn't Stripe work with KSeF directly?
Stripe is an American payment company. The system was not designed for Polish tax regulations. It does not generate invoices in the XML format required by KSeF. It does not support Polish VAT rates or the formal requirements of Polish invoices.
You have three options: issue invoices manually (time-consuming with a larger number of transactions), outsource it to an accountant (additional cost), or use a middleware application that automates the entire process.
How does integration through the S2K middleware app work?
The S2K app connects Stripe with KSeF and automates the invoicing process:
- Customer pays in your store through Stripe
- The app retrieves payment data
- Generates a structured invoice (XML format)
- Sends the invoice to KSeF
- The KSeF system delivers the invoice to the recipient
The entire process happens automatically, without your involvement.
What does S2K - Stripe to KSeF app offer?
S2K is a dedicated application available directly in the Stripe app marketplace.
Installation takes just a few minutes. You connect Stripe with S2K, provide the API key, and configure the webhook. The app works from within the Stripe dashboard – you don't need to install additional tools or export data.
Choice of operating mode. S2K allows you to send invoices manually with one click or completely automatically. You decide how much control you want to maintain over the process.
Status monitoring. The app lets you track invoice statuses, download UPO (Official Receipt Confirmation), and check which documents have been accepted in KSeF.
Regulatory compliance. S2K uses the current structured invoice schema required by KSeF and maintains compliance with the system API.
What data is needed?
S2K uses data necessary to issue invoices in KSeF: email, first and last name or company name, address, and tax identification number (NIP). The system only processes invoices with a Polish NIP – other invoices do not need to go to KSeF.
Technical requirements
To start using the integration, you need:
- Active Stripe account
- Access to KSeF (you can set it up for free at podatki.gov.pl)
- Method of authentication in KSeF
For KSeF authentication, you can use a qualified certificate or trusted signature.
Frequently asked questions
Does the integration work with subscriptions?
Yes. Each recurring payment in Stripe can generate an invoice – automatically or after approval (depending on the selected mode).
Which invoices go to KSeF?
Only invoices with a Polish NIP (VAT ID) are sent to KSeF in accordance with legal requirements. Invoices for customers outside Poland are not subject to this obligation.
KSeF implementation deadlines – when do you need to be ready?
From February 1, 2026, the obligation to issue invoices in KSeF applies to companies whose sales in 2024 exceeded 200 million PLN. From April 1, 2026, the obligation covers all other entrepreneurs.
Important information: the obligation to receive invoices through KSeF applies to all entrepreneurs starting February 1, 2026, regardless of whether they issue invoices in the system themselves. If your contractors (utility providers, telecommunications, fuel suppliers) start issuing invoices in KSeF, you must be able to receive them.
Until the end of 2026, taxpayers can issue invoices outside KSeF if the total sales value documented by these invoices in a month is less than or equal to 10,000 PLN.
How to get started?
The S2K app is currently in beta phase. The planned full release is March 5, 2026, and the KSeF obligation comes into effect on April 1, 2026. You can join the beta testing and prepare your business before the final deadline.
You can find more information on our website or on the project's Discord server, where you can get direct support from the app creators.
