Service / End to end, one contact

KSeF integration: shop, invoicing software and KSeF API

Invoices from your shop, invoicing software or custom system reach KSeF automatically, with the KSeF number on the order.

  • Plugin or invoicing software setup
  • Corrections, returns and invoices for receipts
  • KSeF number and status on the order
  • KSeF API for custom systems and ERP
Ask about KSeF integration

Free first call · I usually reply within 2 h

Vlad Sedenko

Vlad Sedenko

Your online partner at every stage · 12+ years

LinkedIn ↗
12+
years in websites, apps and marketing
150+
projects: I help at every stage, from idea to growth
2–6 wks
from idea to a working product
2 h
usual time to my reply

Pricing

Packages

  • Ready-made integration

    Individual quote

    from 1 working day

    A shop and invoicing software that already integrate with KSeF.

    • Plugin or invoicing software setup
    • NIP on the order and B2B invoices
    • Test in the KSeF test environment
    • Guide for you and your accountant
    Ask about this package

  • Shop KSeF integration

    Individual quote

    from 1 week

    A shop with cases the ready-made plugin doesn't handle.

    • Everything in Ready-made integration
    • Corrections, returns, invoices for receipts
    • KSeF number and status on the order
    • Error alerts and offline mode
    Ask about this package

  • KSeF API integration

    Individual quote

    from 2 weeks

    A custom system, ERP, CRM or web application.

    • Sending invoices, statuses, KSeF number and UPO
    • Token or certificate authentication
    • Queue, retries and logs
    • Optional receiving of purchase invoices
    Ask about this package

What clients say

  • „We worked with Vlad on a Next.js project. He knew what he was doing from day one, didn't overcomplicate things and came up with better approaches on his own. I especially value his work on the site's performance. Everything was delivered as agreed.”

    George B. CEO, finance company

  • „We needed to build an MVP fast to test our idea in practice. Vlad helped us choose sensible solutions and focus on what we really needed for launch. We didn't try to build everything at once, yet he made sure the project could grow later without starting from scratch.”

    Alex N. Product Manager at StartupX

  • „Vlad got up to speed with our project quickly and pointed out several problems we hadn't treated as priorities. He sorted out our database and security issues. I liked that he didn't just complete tasks but clearly explained why something was worth changing and what the consequences could be.”

    Michał R. CTO at TechCorp

  • „We had an app where every bigger change was becoming a problem. Vlad helped us clean up the code, rebuild some of the older parts and introduce automated tests. Working on new features is much easier now. I also appreciate his patience in explaining technical topics to people outside the development team.”

    Sara K. Product Owner at WebSolutions

Find out what your shop needs

Tell me what your shop runs on and which invoicing software you use. I'll reply whether a setup change is enough and what it costs.

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Frequently asked questions

When did KSeF become mandatory?

Large companies (2024 sales above PLN 200 million) have issued invoices in KSeF since 1 February 2026, other VAT payers since 1 April 2026. Deadlines for the smallest businesses and for penalties have already been changed, so check the current status on ksef.podatki.gov.pl or with your accountant.

Does an online shop have to issue invoices in KSeF?

Invoices to Polish businesses (B2B, with the buyer's NIP) generally yes, although there are exceptions, for example for some foreign buyers. The obligation doesn't cover invoices to consumers, but many shops issue all invoices through one process. Agree the setup for your case with your accountant; I implement it technically.

I already have a KSeF plugin or invoicing software. Why would I need help?

Ready-made integrations handle the standard scenario. Problems start with the NIP on the order, corrections and returns, invoices for receipts, sending errors or a custom shop. I find where the process breaks and fix the settings or build the missing part.

Which systems do you work with?

WooCommerce and WordPress, PrestaShop, Shoper (via API), custom shops and web apps (Laravel, Next.js). Invoicing software: Fakturownia, wFirma, inFakt, iFirma and others with an API. ERP systems such as Subiekt, Optima or Comarch after checking what integration options they offer.

I take payments through Stripe. How do I send invoices to KSeF?

Stripe doesn't send invoices to KSeF. The simplest route is to connect Stripe to invoicing software that integrates with KSeF (Fakturownia, for example, has a ready-made Stripe app) and turn off Stripe's PDF invoices so customers don't get two documents. For subscriptions, refunds and custom rules I build an integration on Stripe notifications (webhooks): payments and refunds trigger the invoicing and correction process you agreed with your accountant.

What happens when KSeF is down?

The rules include offline modes. The invoice must reach KSeF later, and its printout must carry QR codes. I set up the process so the shop keeps issuing invoices and the system resends them and stores the KSeF number automatically.

How much does KSeF integration cost?

I give the exact price after a short description of your shop and invoicing software.

How long does it take?

Setting up a ready-made integration usually takes from 1 working day, a shop integration with non-standard cases from 1 week, and a KSeF API integration for a custom system from 2 weeks. I confirm the exact timeline before we start.

What does ongoing support after launch cover?

I adapt the integration when KSeF changes its API or invoice schema, and make small fixes. Support is monthly, with no long contract.

I usually reply within 2 hours.