KSeF and your online store: WooCommerce invoices from 2026

KSeF and your online store in 2026? You can’t put this off any longer. If your store is a VAT payer and issues invoices, it is joining the National e-Invoicing System (KSeF), and invoices from WooCommerce or PrestaShop have to reach it in structured form. It’s January 2026, so there are only a few weeks left. That’s the time you have to check your deadline, the data in your order form and the tool that sends your invoices. Everything below is based on the rules published by the Polish Ministry of Finance. One more thing: this is not tax advice. You still need to talk through your company’s situation with your accountant.

When does mandatory KSeF apply to your store?

Most small and medium stores become subject to the obligation on 1 April 2026. That is what the scope of mandatory KSeF published by the Ministry of Finance says. There is an exception: businesses whose invoiced sales do not exceed PLN 10,000 gross per month don’t have to issue invoices in the system until the end of 2026. Taxpayers using the exemption under Article 113a(1) of the Polish VAT Act (the SME scheme) also stay outside KSeF. And if you’re not obliged? You can still use the system voluntarily, nothing stops you.

Which of these cases fits your business is for your accountant to decide. Don’t guess. A store with seasonal sales can easily go over the limit in December and come nowhere near it in February. That’s why I always base this decision on real figures from the records, not on rough estimates.

Which store documents go into KSeF and which do not?

VAT invoices and their corrections go into KSeF. But several documents that come up all the time in e-commerce stay outside the system. If your store sends a proforma for prepayments, that’s good news. These stay outside KSeF:

• proforma invoices,
• internal invoices,
• internal documents,
• credit notes,
• debit notes.

KSeF in WooCommerce and PrestaShop: what changes in the order process

A PDF in an email no longer closes the matter. The store or the invoicing software has to send the invoice to KSeF and receive the number assigned there. Only then does the document formally exist, and the buyer can download it from the system. In practice this means one thing: a data error shows up when the invoice is sent, not a week later when your accountant starts calling.

So your checkout has to collect data properly. The NIP (Polish tax ID), company name, address. And above all, a clear distinction: business customer or consumer? There are usually several touchpoints (and each one can break something): an invoicing plugin in WooCommerce or a module in PrestaShop, external accounting software that receives the orders, or simply a manual export. Returns and contract withdrawals also go through the system, because a correction of a structured invoice is sent to KSeF too.

How to prepare e-invoicing in your store step by step

In general it comes down to three things: your deadline, the tool that sends invoices and a test of the whole flow before the obligation starts. Broken down into steps, it looks like this:

1. Confirm your deadline with your accountant and check whether you fall under the invoiced sales limit.
2. List where invoices are created today: in the store, in accounting software or by hand.
3. Check whether your plugin or software supports sending to KSeF.
4. Clean up the NIP and company data fields in your order form.
5. Test sending an invoice, a correction and returns from the withdrawal form.
6. Decide who in the company keeps an eye on invoices rejected by the system.

Step three. In my view, what matters most here is whether the tool is updated at all, because an abandoned plugin and KSeF are asking for trouble. K4.pl, a shop with WooCommerce plugins and PrestaShop modules run by Web Systems, sells licences with updates and support. For unusual invoice flows it also builds custom plugins.

Invoices with attachments and other KSeF changes in 2026

From 1 February 2026 you can send invoices with an attachment to KSeF. It’s optional, and most stores won’t touch it at all. It was designed for utility, telecom and fuel suppliers, that is, those who issue invoices with detailed price and quantity data. The attachment is an integral part of the invoice. It can contain only mandatory invoice elements and data closely related to them, no marketing. The feature works after you register for it in e-Urząd Skarbowy (the tax office’s online portal), and registrations are accepted from 1 January 2026.

Do you sell to schools, government offices or other public bodies? Then it’s worth knowing that B2G invoices issued on the PEF platform are treated as structured invoices once they are sent to KSeF and receive a number.

For an online store, KSeF is mostly about getting the process in order. Check your deadline on the Ministry of Finance website, sort out the data collected at checkout, and test sending invoices and corrections before the obligation kicks in. The sooner the flow works on test orders, the calmer your first month will be. There’s no point in waiting.

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