KSeF · mandatory now · penalties from 1 Jan 2027
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
5265877635-20260604-0A1B2C3D4E5F-12
You're KSeF-compliant for this invoice. The UPO is the official proof of acceptance — keep it.
- Free in production
- Built into Stripe
- On your servers — no recurring fees
Here's the bind you're in.
You invoice through Stripe. KSeF is already mandatory — every B2B invoice has to reach the government system in FA(3) format, and you have to keep the UPO (the official proof of acceptance). Stripe doesn't do any of that. And on 1 January 2027, the penalties kick in.
Sounds like a lot. It isn't, with us.
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. You invoice the way you always have. We handle the rest, and we show you the proof.
— 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
5265877635-20260604-0A1B2C3D4E5F-12
You're KSeF-compliant for this invoice. The UPO is the official proof of acceptance — keep it.
Every invoice ends in an official UPO — the KSeF number in monospace, copyable, never cut off. That's your proof of compliance. 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 (metadata and invoice footer). 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 — and that's exactly what we're built to get right.
- Is the free plan really free?
- 10 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 the NIP against GUS on every invoice — before KSeF would reject it.
- Can I self-host?
- Yes — on your own servers, one-time, no recurring fees.
Convinced? 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 1500 zł net — one-time. No subscription. Your code and data stay with you.
Your data is yours.
Export UPOs and invoices anytime, self-host, no lock-in. Don't want to host it yourself? We can deploy KSeF Kit on your servers.
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 (and, on the cloud edition, 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 · 10 invoices/mo
- KSeF + UPO
- Credit notes (KOR)
- NBP FX, NIP, reverse charge, export of services
- Runs on your own servers too
Overage: 0.05 zł/invoice — we won't block a legal filing just because you hit a plan limit.
Prefer your own servers? We'll deploy KSeF Kit on your infrastructure for 1500 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 — the structured format the regulations require.
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 — exactly as the VAT and KSeF rules require. Example: for a $1,000 invoice issued on 5 June, we use the NBP USD/PLN rate from 4 June. 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 — we won't block a legal filing just because you hit one.
When does KSeF become mandatory?
The rollout is phased: large taxpayers from 1 February 2026, all VAT businesses from 1 April 2026, and penalties from 1 January 2027. It pays to be ready early.
Can I self-host KSeF Kit?
Yes. KSeF Kit runs on your own infrastructure — we deploy it on your servers. Your data stays with you, with no vendor lock-in.
Do you have access to my KSeF account?
We keep your KSeF token encrypted (on the cloud edition, 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 — that's exactly the case we're built for. 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 don't want to deploy it myself — can you do it for me?
Yes. We deploy and configure KSeF Kit on your servers for 1500 zł net — one-time, with no recurring fees. Your code and data stay with you. It's the alternative to the subscription cloud.
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