Stripe Integration with wFirma: A Guide for 2026

Introduction — Why Stripe and wFirma?

Stripe is a global payment gateway that enables accepting payments from around the world but does not offer Polish VAT invoice generation or National e-Invoice System (KSeF) support. All Stripe transactions must therefore be separately invoiced in a local accounting system and from 2026 submitted to KSeF.

wFirma is a Polish accounting and invoicing software aimed at micro-entrepreneurs, e-commerce businesses and accounting offices. It offers modules for invoicing, accounting, warehouse and payroll, as well as a broad integration ecosystem. Thanks to partnership with the Apilo platform and dedicated e-commerce integrations, wFirma enables managing sales across multiple channels (Allegro, Shoper, Magento, Prestashop, etc.), with all orders automatically recorded in the system. Additionally, the programme integrates with many fiscal printer models, enables online receipt issuance and connects with the GUS database for automatic contractor data completion.

With the approaching mandatory KSeF, integrating Stripe with wFirma becomes a necessity for businesses selling online. In this article, we explain what KSeF is, present the advantages of wFirma and show how to automate the invoicing process step by step using Striptu — a Polish integrator connecting Stripe with Polish accounting systems.

What is KSeF?

The National e-Invoice System (KSeF) is a central IT system where entrepreneurs issue, send, receive and store structured invoices. Each invoice receives a unique identification number and is stored in the government archive for at least 10 years. The implementation aims to digitise document workflows, reduce errors and increase tax control.

The Ministry of Finance has set the following mandatory KSeF deadlines:

- 1 February 2026 — mandatory for companies with 2024 sales (including tax) above 200 million PLN.
- 1 April 2026 — mandatory for all other entrepreneurs.
- Micro-entrepreneurs with monthly sales up to 10,000 PLN may use a transitional period until 1 January 2027.

Entrepreneurs must submit every sales invoice to KSeF almost immediately after issuance. The system also allows receiving purchase invoices. Using KSeF-integrated accounting software (like wFirma) greatly simplifies these obligations.

Why Stripe cannot issue a Polish invoice or submit it to KSeF

Stripe focuses on payment processing. Transaction confirmations sent to customers ("receipts") do not contain the buyer's NIP number, the correct VAT rate or numbering compliant with Polish regulations and are not structured e-invoices. Stripe does not offer KSeF integration, so every sale must be separately invoiced in a Polish system and the invoice submitted to the government register. Manually re-entering data from hundreds of transactions is laborious and risky, so it is worth automating the process with wFirma and Striptu.

wFirma — what makes this system stand out?

wFirma is a comprehensive invoicing, accounting and payroll system. Its most important features for online sellers and entrepreneurs include:

- Multi-channel sales and e-commerce integrations — wFirma integrates with the Apilo platform and many online shops (Shoper, Clickshop, Magento, Prestashop, Redcart, CScart, CStore, etc.), enabling multi-channel sales management. All sales are automatically recorded in the system.
- Fiscal printer and e-receipt integration — the programme supports numerous printer models, enabling fiscal receipt issuance directly from the system. It also works with eparagony.pl for emailing receipts to customers.
- Automatic contractor data completion — wFirma connects with the GUS database; after entering a NIP number, the programme automatically fills in the contractor's name and address, speeding up invoice issuance.
- Full KSeF integration — wFirma has offered automatic structured invoice support since March 2023. The system enables both sending and receiving e-invoices from KSeF without external tools. Users can specify whether to automatically retrieve purchase invoices, send B2B/B2C sales invoices and receive sales invoices. Before KSeF 2.0 goes live, wFirma encourages uploading certificates or tokens; once in place, the system will automatically connect to KSeF on 1 February 2026.
- Attractive pricing — the Invoicing and CRM package costs 19 PLN net per month and includes e-commerce integrations, mini warehouse, contractor monitoring, automatic and recurring invoices, JPK_FA, fiscal printer support and SMS notifications about issued invoices.

Thanks to these features, wFirma is a comprehensive solution for online sellers, preparing its customers for mandatory KSeF.

How to integrate Stripe with wFirma using Striptu — step-by-step guide

Striptu is a Polish SaaS system that connects global payment platforms (Stripe, Kajabi, ThriveCart) with domestic accounting systems. Our tool receives payment information from Stripe, creates an invoice in wFirma and forwards it to KSeF. The integration is simple and requires no technical knowledge.

Step 1 — Create a service in Striptu and connect your Stripe account

Register on Striptu and create a new service. During configuration, provide the Secret API Key from the Stripe dashboard. Our tool will automatically set up the webhook that will relay transaction information.

Step 2 — Connect Striptu with wFirma

After activating the wFirma integration in the Striptu wizard, go to the Settings tab and in the wFirma section enter the required data:

1. API Token (access key) and API Token (secret key) — in wFirma, API keys are created in the account settings menu. After logging in, click your name in the upper right corner, go to Security > Applications and in the API Keys tab generate a new connection. Copy both tokens and enter them in Striptu. More about wFirma API token configuration in the documentation.
2. Click Test connection to verify the data. Step-by-step instructions are available in the documentation.

Step 3 — Configure additional options

- Default income tax rate (flat-rate) — if you settle on a flat-rate basis, you can set a default rate in Striptu. It will be passed to wFirma with the invoice. More about flat-rate configuration in the documentation.
- Automatic invoice email sending — enable automatic PDF sending to the customer. This feature requires an active email module in wFirma. Details about automatic email sending here.
- Default VAT rate — if you do not use the Stripe Tax module, Stripe does not pass the net amount. In this case, set a default VAT rate in Striptu (e.g. 23%) so the programme calculates net and VAT values on the invoice.

After saving the settings, make a test transaction in Stripe test mode. Check whether the invoice was correctly issued in wFirma, whether it contains all data and whether it was sent by email and to KSeF. Then switch to production mode.

Why you should not integrate Stripe with KSeF yourself

Although both Stripe and KSeF provide APIs, independently connecting these systems is complex and expensive to maintain. It requires generating e-invoices in XML format compliant with the FA schema, authenticating submissions with a Trusted Profile or certificates, updating schemas when regulations change and securing keys. For most micro-businesses, such investment is not worthwhile. Using ready-made integrations (wFirma, Striptu) lets you focus on business, not programming.

Benefits of Stripe → wFirma → KSeF automation

- Time savings — invoices are issued automatically after each payment. The process is fully automated, eliminating manual data re-entry.
- Compliance with Polish law — wFirma has a certified KSeF integration, guaranteeing that documents are sent and received in the required format. More about compliance in our article.
- Fewer errors — customer data (amount, NIP, address, VAT rate) is transferred automatically, minimising mistakes. Every transaction is automatically invoiced.
- Fast document delivery — wFirma can send the invoice PDF via email to the customer and simultaneously submit the e-invoice to KSeF. This speeds up the document workflow.
- Future-readiness — integrating Stripe with wFirma and KSeF in advance allows testing processes, catching errors and entering the mandatory system stress-free in 2026. The first 10 transactions in Striptu are free, making it easy to test the integration.

Summary

KSeF implementation is a revolution in Polish invoicing. From February and April 2026, entrepreneurs will be required to issue e-invoices and submit them to the government register almost immediately after sale. Stripe does not provide VAT invoices or KSeF integration, so the most sensible solution for online sellers is to use a Polish accounting system with KSeF support.

wFirma is a comprehensive tool with an e-commerce module, Apilo integration, fiscal printer support and full KSeF compatibility. With Striptu, you can connect Stripe with wFirma in a few simple steps: generate API keys in wFirma, enter them in Striptu, set tax preferences and make a test transaction. Full configuration instructions are available in the documentation. After integration, every Stripe payment automatically creates an invoice in wFirma, sends it to KSeF and delivers it to the customer, saving time, minimising errors and ensuring legal compliance.

If you sell online and use Stripe, do not wait until the last moment. The integrated Stripe → wFirma → KSeF solution will give you peace of mind, comfort and a competitive edge in 2026.