An invoice at the moment of sale
An order, a subscription renewal or a refund creates an invoice or a correction in KSeF straight away. No waiting for month-end.
Integration with Poland’s National e-Invoicing System
KSeF invoices straight from your own system.
Your store, subscriptions or custom app issue a structured invoice, send it to KSeF and store its number. Your accountants get everything, and nobody retypes data by hand. Built for companies selling to Polish businesses.
Projects from €1,500 net. The first version usually takes 2–3 weeks.
Your systemStore, Stripe, app or ERP
- Invoices and corrections
- KSeF number and receipt
- Purchase invoices
IntegrationFA(3) · Queue · Retries · Logs
- Invoices and corrections
- KSeF number and receipt
- Purchase invoices
KSeFNational e-Invoicing System
Benefits
Compliance without manual work.
One source of data
Buyer details, line items, VAT rates and payments come from the system where the sale happened. They never drift from the books.
Calm after an outage
If KSeF or the network stops responding, the invoice waits in a queue and is sent again. Every submission has a status and a KSeF number in the log.
From front-end tasks all the way to deeper checkout flows that required API work with product, Arek consistently delivered A+ work, quickly.
Who it’s for
When an off-the-shelf plugin isn’t enough.
Subscriptions and recurring payments
Invoices for every renewal, plan change and refund from Stripe or another gateway, with the right VAT for business customers.
Custom apps and platforms
A customer portal, marketplace or booking system that calculates its own prices and has no invoicing module.
Several systems at once
Sales in the store, in an app and in the ERP, with invoices sent to KSeF from one place and no duplicates.
Receiving purchase invoices
We pull purchase invoices from KSeF into your system or a spreadsheet, so your accountants don’t have to look for them.
What the project covers
From a data map to an invoice with a KSeF number.
Sales and data review
We check where sales happen and what data you already have. We agree which documents go to KSeF, in what order and who owns them.
KSeF API connection
We build the invoice in the FA(3) schema, authenticate with a token or certificate and send it to KSeF. The number and receipt are stored with the order.
Queue and fallback
Submission runs in the background and doesn’t slow the store down. Errors come back with a description, and documents wait for a retry instead of disappearing.
Testing and launch
We test on the KSeF test environment with your data, then switch to production. We stay with the integration when the Ministry of Finance changes the schema.
How we work
From a list of documents to working submission.
We work with you from the first conversation to launch. We’ve delivered more than 100 commercial projects for companies in Poland, Germany and the US, and we bring in specialists with the experience your project needs.
- 01
List of documents
With you and your accountants, we agree where sales happen, which documents go to KSeF and how corrections work.
- 02
Testing in the KSeF environment
We send invoices to the KSeF test environment using your data. We check the numbers, receipts and behaviour during outages.
- 03
Production and schema changes
We switch submission to production and keep an eye on the logs. When the Ministry of Finance changes the schema, we update the integration.
FAQ
The KSeF questions we hear most often.
Does KSeF apply to my company?
It applies to VAT payers established in Poland, including Polish branches and fixed establishments of foreign companies. Check your case with a Polish tax adviser.
When did KSeF become mandatory?
Large companies have issued invoices in KSeF since 1 February 2026, everyone else since 1 April 2026. The smallest taxpayers have until 1 January 2027. Confirm the details and penalty dates with your adviser, because the rules are still changing.
Do you handle corrections and refunds?
Yes. A refund in the store or in Stripe creates a corrective invoice linked to the original in KSeF.
Do you give tax advice?
No. We build the integration to the rules you agree with your accountant or tax adviser. We are happy to talk to them directly.
How much does a KSeF integration cost?
Projects start at €1,500 net. The price depends on how many sales sources there are, which document types you need and whether we also pull purchase invoices. After a short review, we give a fixed price for the first version.
Contact
Still issuing invoices by hand?
Tell us where your sales happen and which accounting system you use. We’ll tell you whether an off-the-shelf plugin will do or you need an integration.