KSeF · mandatory now
File your Stripe invoices to KSeF, automatically.
Finalize an invoice in Stripe and we file it to KSeF in seconds, then write the KSeF number straight back to Stripe. Free production plan, no card.
Filed
Your invoice is in KSeF. You have the UPO.
KSeF number
1111111111-20260604-0A1B2C3D4E5F-12
The UPO is the official proof of acceptance — keep it.
- Free in production
- Built into Stripe
- On your servers — no recurring fees
Stripe doesn't file your invoices to KSeF.
You invoice through Stripe. KSeF is already mandatory — every B2B invoice you issue has to reach the government system in FA(3) format, and you have to keep the UPO (the official proof of acceptance). Penalties are due on 1 January 2027, and a government bill would push them back a year.
You invoice the way you always have. We handle the rest.
KSeF Kit connects to Stripe and takes KSeF off your plate: FA(3) conversion, filing, the UPO, and the KSeF number written back to Stripe — whether you're billing a Polish company, an EU business, or a client overseas.
— the KSeF Kit team
Proof from the tax office
Don't take our word for it. Take the tax authority's.
Filed
Your invoice is in KSeF. You have the UPO.
KSeF number
1111111111-20260604-0A1B2C3D4E5F-12
The UPO is the official proof of acceptance — keep it.
Every invoice ends in an official UPO with the KSeF number. We keep every UPO, and you can export them all for your accountant in one click.
How it works
Three steps, then nothing to do.
Connect Stripe
One-click install. No API keys, no code.
The invoice goes to KSeF
Finalize an invoice in Stripe and we convert it to FA(3), file it, and wait for the UPO.
You get the UPO
We write the KSeF number back to Stripe (invoice metadata) and show it in the panel. The UPO is ready to download and archive.
No compromises
Corrections, FX, reverse charge, export — all handled.
Most integrations handle a plain domestic invoice. The hard part is corrections, foreign currency, reverse charge, and selling abroad.
- Is the free plan really free?
- 6 invoices a month, in production, no card.
- Credit notes (KOR) too?
- Stripe credit note → FA(3) KOR, automatically.
- Foreign-currency invoices?
- Converted at the NBP average rate (table A) from the last business day before issue — just as the rules require.
- Domestic reverse charge?
- Marked correctly on the FA(3) (reverse-charge flag).
- Selling abroad — EU and beyond?
- We cover how you really invoice across borders: domestic B2B (23% and reduced rates), EU reverse charge (your EU business customer accounts for the VAT), and export of services outside the EU — your Polish one-person shop billing a US SaaS. The right FA(3) markings and NBP FX are applied for you.
- NIP validation (GUS / whitelist)?
- We check your company NIP against the MF whitelist during setup. If a buyer NIP is wrong, KSeF rejects the invoice with code 21301 and we show you what to fix in Stripe.
- Can I self-host?
- Yes — on your own servers, one-time, no recurring fees.
Connect Stripe and file your first test invoice in a minute.
Start for freeTrust, built in
Your data, your infrastructure — or our cloud.
Deployed on your servers — no recurring fees.
We set up and configure KSeF Kit on your own infrastructure for 2500 zł net — one-time. Your code and data then stay with you.
Your data is yours.
Export UPOs and invoices anytime, no lock-in.
Test mode is impossible to miss.
You'll never mistake a test for a real filing.
Your KSeF token is encrypted.
We keep your KSeF token encrypted on our side (if you installed the Stripe App, in Stripe's Secret Store) and use it only to file your invoices.
Pricing
Every plan files for real. Start for free.
You pay only for higher invoice volume and support — never for compliance.
Free
0 zł / mo
no card · 6 invoices/mo
- KSeF + UPO
- Credit notes (KOR)
- NBP FX, NIP, reverse charge, export of services
- Runs on your own servers too
Above the limit, invoices wait in the queue. Nothing is lost, and we file them automatically once you raise the limit.
Prefer your own servers? We'll deploy KSeF Kit on your infrastructure for 2500 zł net, one-time — no recurring fees.
FAQ
Before you ask
Is this compliant with KSeF 2.0?
We file FA(3) (schema 1-0E) directly to KSeF 2.0 and return the official UPO.
Do I need a card for the free plan?
No. The free plan runs in production with no card. You only add a card when you move to a paid plan.
What about invoices in EUR, USD or other currencies?
We convert them to złoty at the NBP average rate (table A) from the last business day before the invoice issue date , as the VAT Act requires. Example: for a $1,000 invoice issued on Thursday 12 March 2026, we use the NBP USD/PLN rate from Wednesday 11 March. We never use Stripe's settlement FX rate.
Do you handle credit notes (KOR)?
Yes. A Stripe credit note becomes an FA(3) KOR that references the original KSeF number.
What if KSeF rejects an invoice?
We show the reason in plain Polish and the exact next step. Resubmit in one click.
What if I hit my plan limit?
Invoices stay queued and file as soon as you raise the limit.
When did KSeF become mandatory?
KSeF is already mandatory: from 1 February 2026 for businesses with 2024 sales above 200 million zł, and from 1 April 2026 for all other VAT payers, VAT-exempt ones included. Sellers whose KSeF-covered sales are at most 10,000 zł a month may wait until 1 January 2027. Penalties apply from 1 January 2027 unless a government bill moving them to 1 January 2028 becomes law.
Can I self-host KSeF Kit?
Yes. We deploy KSeF Kit on your servers. Your data then stays with you, with no vendor lock-in.
Do you have access to my KSeF account?
We keep your KSeF token encrypted on our side (if you installed the Stripe App, in Stripe's Secret Store) and read it only to file your invoices to KSeF on your behalf. Nothing else, and on the self-hosted edition the token never leaves your server.
I sell abroad — does this fit how a Polish founder bills foreign clients?
Yes. We cover domestic Polish B2B at 23% VAT (and reduced rates), EU reverse charge — your EU business customer accounts for the VAT — and export of services to non-EU clients, the classic Polish solo dev or studio billing a US SaaS. The right FA(3) markings and the NBP FX conversion are applied for you in each case.
I sell through Stripe Managed Payments. Does that go to KSeF?
By default, no. With Managed Payments, Stripe (as Sold through Link, LLC) sells to your customers and invoices them, and your sale to Stripe is documented by a self-billed invoice that Stripe issues on your behalf. A self-billed invoice from a foreign buyer that doesn't use a Polish NIP is issued outside KSeF, and it may not be filed there even voluntarily — Polish tax rulings of 27 March 2026 (0112-KDIL1-3.4012.73.2026.1.KK) and 7 August 2026 (0112-KDIL1-3.4012.378.2026.1.ŁW) confirm it. Stripe's terms do let you opt out of self-billing, though: then you invoice Stripe yourself, and that invoice goes to KSeF like any other B2B invoice you issue. KSeF Kit is for the invoices you issue yourself. It doesn't yet recognise the invoices Stripe issues to your customers and could file them to KSeF under your NIP, so if you use Managed Payments, don't connect that Stripe account until you've written to us.
I don't want to deploy it myself — can you do it for me?
Yes. We deploy and configure KSeF Kit on your servers for 2500 zł net — one-time, with no recurring fees.
Will you file invoices I issued before installing?
No. We file invoices finalized in Stripe after you connect your account. File the earlier ones in KSeF yourself, for example in the KSeF taxpayer app. We won't file them later either, so there's no duplicate. A correction to such an invoice goes in by hand too.
KSeF-ready in a minute — before the penalties hit.
Connect Stripe and file your first test invoice in a minute.
No card · No commitment · Or on your own servers