How to Quickly Get KSeF Up and Running in a Startup?

The National e-Invoice System (KSeF) is a government platform that introduces a real revolution in the Polish invoicing system. Instead of traditional paper invoices or PDF files sent by email, in KSeF all invoices become structured XML documents processed through a central government system. Every invoice must be submitted to KSeF before reaching the counterparty and will receive a so-called Official Acknowledgment of Receipt (UPO) confirming registration in the system. For entrepreneurs – including young companies and startups – this means a fundamental change in how sales are documented and a new obligation to adapt to a uniform e-invoice standard. Below we explain what exactly KSeF involves, when it becomes mandatory, and how to quickly implement it in a startup, especially when you use modern sales platforms like Stripe or Kajabi.

What Is KSeF and Who Does It Apply To?

KSeF is the Ministry of Finance's central system where ultimately all invoices issued by businesses in Poland will be registered. In practice, this means transitioning from any invoice format (paper, PDF) to a single unified XML format (FA(3)) mandated by the Ministry of Finance. Every entrepreneur, regardless of company size, will be required to issue structured invoices through KSeF or via software integrated with KSeF. This applies to all VAT-taxable transactions in Poland – domestic sales of goods and services, both B2B and to public entities. KSeF is meant to streamline document flow, eliminate manual data entry, and speed up settlements. Importantly, this system opens the door to full invoicing automation – invoices can be generated and sent automatically from financial systems, meaning huge time savings and fewer errors. For businesses, it's an opportunity to reduce bureaucracy and focus on the business, but it requires prior preparation and the right tools.

When Will KSeF Become Mandatory for Startups?

KSeF implementation has been phased by company size. Large enterprises (with annual sales > 200 million PLN) will be the first to face the obligation – from February 1, 2026. Other entrepreneurs, including small and medium businesses and sole proprietorships (JDG) – effectively most startups – will be covered from April 1, 2026. This means startups have until the end of March 2026 to implement e-invoicing via KSeF. However, it's worth preparing earlier, especially since regulations provide severe consequences for non-compliance. While the smallest micro-businesses achieving very low revenues (up to 10,000 PLN monthly) will receive a full exemption until the end of 2026, exceeding the 10,000 PLN monthly sales threshold immediately triggers the loss of the right to paper invoices – from that transaction onwards, invoices must go through KSeF. From 2027, the system will cover absolutely everyone. Additionally, from 2027, severe financial penalties for non-compliance will apply – up to 100% of the VAT amount or 18.7% of the transaction value. A missing KSeF invoice can also mean settlement problems: the invoice recipient cannot deduct VAT or count the expense as a tax-deductible cost if the invoice isn't registered in KSeF. Therefore, for startups, quickly getting KSeF sorted is crucial to avoid penalties and business disruptions.

Selling Through Stripe and Invoice Issuance in Poland

Many young internet companies monetize their products through global platforms. Stripe – an international payment platform – is enormously popular among SaaS startups, online course creators, and digital tool providers. Even the largest tech companies trust this solution: over 1.35 million websites worldwide use Stripe for payment processing, and the service handles transactions for half of the Fortune 100 companies. Moreover, 78% of the fastest-growing AI companies (Forbes AI 50) also rely on Stripe infrastructure. It's no wonder that Polish startups also reach for Stripe, especially those selling digital content globally. E-commerce and educational platforms like Kajabi, LearnWorlds, Web2Learn, EasyTools and paid community systems often integrate with Stripe to facilitate creators accepting payments worldwide. Even innovative developer services (e.g., Replit) or AI coding tools (like Lovable, Cursor) use Stripe for online billing.

However, it's important to remember that Stripe only handles the payment – it doesn't issue invoices compliant with Polish regulations. If your startup sells products or services and accepts payments through Stripe (or a similar foreign system), you must ensure a legal VAT invoice is issued for every transaction. Many online creators initially do this manually: exporting the payment list from Stripe weekly and manually entering data into invoicing software or – worse – issuing invoices one by one in Word or Excel. Such manual "paperwork" becomes a nightmare at larger scales. Delays appear, customer data errors occur, significant time is wasted, and the risk of KSeF non-compliance grows. Fortunately, there are ways to automate invoicing for Stripe sales – so your startup can focus on the product while invoices "create themselves" in compliance with Polish law.

Automating KSeF in a Startup – How to Implement Quickly?

Since KSeF will become mandatory, the best approach for a startup is automating the entire invoice issuance and delivery process. This way, you'll not only save time but also ensure full compliance from day one of KSeF enforcement. Here's how to quickly get KSeF sorted in a startup step by step:

1. Choose invoicing software with KSeF integration. The simplest way to adapt to e-invoices is to use market-available accounting applications that have already implemented KSeF. Popular Polish systems like Fakturownia, inFakt, wFirma, ifirma, etc. are working on full integration – e.g., Fakturownia has already released XML export for KSeF structure and is testing an automatic invoice submission module for KSeF following the latest Ministry of Finance guidelines. Using such software ensures your invoices meet KSeF requirements and can be immediately submitted to the system.
2. Gain KSeF access and authorize users. To issue e-invoices, your startup needs KSeF access – meaning an authenticated user (trusted profile, qualified signature, e-ID, or a special KSeF certificate). Designate people (e.g., an employee or accounting firm) who will handle KSeF invoices and grant them permissions through the ZAW-FA form. These formalities are worth completing before the system becomes mandatory, so everything works smoothly on day one.
3. Integrate your sales channel (e.g., Stripe) with invoicing software. If you use Stripe, Kajabi, ThriveCart, WooCommerce, or another sales platform, look for a solution that integrates it with your invoicing program. There are specialized SaaS tools that connect Stripe with Polish invoicing systems – so every payment automatically results in a VAT invoice. For example, integrating Stripe with Fakturownia means invoices are created and sent automatically after every Stripe payment, with no manual steps. Such a module runs in the background and ensures complete documentation – you get the certainty that every customer receives an invoice and all sales are invoiced according to law. Importantly, such solutions work with KSeF modules in accounting software, automatically submitting e-invoices to KSeF or making your invoices ready for later submission. This way, your online sales immediately become KSeF-compliant, even if they're based on foreign payment platforms.
4. Test and monitor the process. After configuration, make a few test transactions, verify that invoices are generated correctly and reach where they should (the customer, KSeF, your accountant). Ensure all required data (buyer, NIP, sales description, VAT rates) transfers correctly. Good integration tools allow a test mode or manual document approval at first – use this to fine-tune settings. When everything works, you can switch to full end-to-end automatic mode. From then on, after every Stripe (or other system) payment, a VAT invoice will be automatically issued in your accounting software and (once KSeF is live) automatically submitted to KSeF, without a single extra click from you.
5. Stay up to date. Finally, follow communications from your invoicing software provider – e.g., Fakturownia and inFakt report on KSeF integration progress. Regularly update these applications to access the latest features. When the full KSeF obligation takes effect in 2026, your system should automatically start submitting invoices to the government repository. It's also worth training your team or accountants on new procedures (e.g., how to download UPO, where to check invoice status in KSeF). Fortunately, after a well-executed implementation, KSeF operations will become largely self-running, and your company will operate in compliance without additional effort.

Summary

Getting KSeF sorted in a startup doesn't have to be difficult or time-consuming if you approach it methodically and use available tools. KSeF introduces a uniform e-invoice standard that may initially seem like another bureaucratic requirement, but in reality can streamline company finances and save a huge amount of time through automation. For young companies, the key is to quickly adapt to the new regulations – the obligation for most of them arrives as early as April 1, 2026. Fortunately, instead of building complicated solutions independently, a startup can use ready-made integrations. Combining systems like Stripe or Kajabi with a Polish invoicing program (with KSeF support) enables issuing invoices completely automatically and in compliance with the law. This in turn means that founders and creators can focus on business growth, while e-invoicing "happens" in the background, eliminating manual paperwork. The sooner you implement such solutions, the more smoothly your startup will enter the new KSeF era – without stress, without penalties, and without unnecessary manual work. KSeF automation is an investment that will pay off with peace of mind, time savings, and full compliance from day one of the new requirements.