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From 1 January 2027: the KSeF number in the bank-transfer title (Art. 108g, Polish VAT Act)

KSeF 2.0 integration for companies with their own systems

Your system and KSeF — connected.

I connect your ERP, online shop or custom software to KSeF — sending and receiving FA(3) invoices, statuses and UPO, and from 2027 the KSeF number in bank transfers. No need to replace the system you use.

2027 package — fixed price

No obligation. I usually reply within 1 business day.

  • RAEOLAS · Pobiedziska, Wielkopolska
  • Tested on the KSeF test environment (API 2.0)
  • FA(3) XML validated against the official XSD schema

Who it's for

Who this service is for

It's for you if…

  • your invoices come out of your own system — an ERP, WMS or custom software,
  • your online shop runs on its own engine, or on a platform without built-in KSeF,
  • you're a software house and your clients are asking about KSeF,
  • your software vendor has no plans for KSeF integration, or keeps postponing it,
  • you want purchase invoices from KSeF to land in your system automatically.

It's not for you if…

  • you invoice in inFakt, wFirma, Fakturownia or a similar program — they already support KSeF, so you don't need me,
  • you issue a few invoices a month — the Ministry of Finance's free tools (Aplikacja Podatnika KSeF 2.0) are enough,
  • you're looking for invoicing software — I don't sell any.

Scope

What I connect

Your system keeps doing what it does. I add the connection to KSeF.

Sending FA(3) invoices

An invoice from your system becomes valid FA(3) XML, is encrypted and sent to KSeF.

Receiving invoices

Invoices issued to your NIP are fetched from KSeF regularly and delivered to your system.

Statuses, KSeF number and UPO

Every invoice you send gets its KSeF number and UPO — the official confirmation of receipt — stored with the document.

KSeF number in transfers (2027)

From 1 January 2027 a transfer paying a KSeF invoice must carry its KSeF number. I'll prepare your transfers for it.

On request: offline-mode handling, token and permission management, and rollout on the test environment first.

The 2027 rule

2027: the KSeF number in the transfer title

From 1 January 2027, an active VAT payer paying another active VAT payer for a KSeF invoice must put that invoice's KSeF number in the transfer (Art. 108g of the Polish VAT Act).

  • Paying several invoices in one transfer uses a collective identifier, generated in KSeF.
  • The rule also covers split-payment (MPP) transfers and direct debits.
  • It applies to payment by transfer or another payment instrument — including when a third party pays the invoice.

If your own system creates the transfers — e.g. exports batch files to your bank — it needs preparing for this.

What has to change in your system (in Polish)
Illustrative example — the title field format depends on the bank and the payment method.

KSeF calendar

61days until 1 January 2027

  1. 1 Feb 2026 (passed)

    KSeF mandatory for the largest companies (2024 sales above PLN 200m); from this date everyone receives invoices through KSeF

  2. 1 Apr 2026 (passed)

    KSeF mandatory for all other companies except the smallest

  3. until 31 Dec 2026 (upcoming)

    companies whose invoiced sales don't exceed PLN 10,000 gross a month may still invoice outside KSeF

  4. 1 Jan 2027 (upcoming)

    KSeF mandatory for everyone; the KSeF number in transfer titles

Penalties for KSeF errors: under current law from 1 January 2027, up to 100% of the invoice's VAT. The government has adopted a bill extending the deferral of penalties to 31 December 2027 (status as of October 2026).

Offer

2027 package: the KSeF number in transfers

A fixed price for preparing your system for the Art. 108g obligation — before it applies on 1 January 2027.

Fixed price

PLN 3,900 net

+ 23% VAT

  • Delivered within 15 working days of the signed order and access to your system and the KSeF test environment.
  • 30 days of support after handover — defects in the delivered changes fixed at no extra cost.

Included

  • a review of how your system creates transfers (bank export, bank API, MPP),
  • fetching the KSeF numbers of purchase invoices into your system,
  • the KSeF number or collective identifier in the title of every transfer paying a KSeF invoice,
  • handling of split-payment (MPP) transfers,
  • testing on the KSeF test environment and short documentation of the changes.

Everything else — sending and receiving invoices, UPO, offline mode — is quoted individually after a free call.

Not included: changes on the bank's side, and systems with no API or transfer export.

Process

How I work

  1. 1

    Free call

    30 minutes: what system you have, where invoices and transfers come from, what needs to change.

  2. 2

    Fixed written quote

    Scope, price and timeline — before I start anything. No billing hours after the fact.

  3. 3

    Implementation

    On the KSeF test environment first, then production — on your own tokens or certificates.

  4. 4

    Handover and support

    Code in your repository, documentation, and help after go-live.

Verified

What already works

  • KSeF (the Ministry of Finance test environment) accepted the invoices I sent and issued KSeF numbers for them.
  • The FA(3) XML is checked automatically against the official XSD schema.
  • 15 automated tests guard the FA(3) invoice generator.

KSeF API 2.0 · test environment

200
GET /v2/sessions/{ref}/invoices/{ref}HTTP/1.1 200 OK{  "ksefNumber":    "1234563218-20260925-5177F4000005-FA",  "status": {    "code": 200,    "description": "Sukces"  }}
An invoice-status response, trimmed to the fields the integration stores. The KSeF number was issued by the Ministry of Finance test environment.

FAQ

Frequently asked questions

Do I have to change the system I use?

No. The integration adds a connection to KSeF. Your system keeps issuing invoices and transfers as it does today.

Which technologies do you work with?

My reference implementation is written in TypeScript (Node.js). I can deliver it as a separate service with a simple API that any system can call, or build the integration into your code. We settle the details on the call.

How much does it cost and how long does it take?

The 2027 package has a fixed price. Other work is quoted after a free call — you get a fixed written quote with a timeline.

Where are the KSeF tokens and certificates kept?

The integration runs on your own KSeF permissions — a token or certificate that you issue in the KSeF 2.0 Taxpayer Application and can revoke at any time. Where they are stored and who can access them is agreed in writing before the work starts.

Does the 2027 obligation apply to me?

That's a tax question — best confirmed with your accountant or tax adviser. I handle the technical side of the implementation.

What if the Ministry changes the KSeF API?

KSeF is still changing. You can have post-launch support, under which I adapt the integration to API changes.

Who are you?

FakturAI is a brand of RAEOLAS, based in Pobiedziska, Wielkopolska. I built and tested a KSeF 2.0 connection end to end — from authentication and session encryption, through FA(3) XML, to the KSeF number and UPO.

Contact

Let's talk about your system

Tell me which system you want to connect and what should happen with invoices. I'll reply and suggest a time for a free 30-minute call.

What happens next

  1. 1I reply to your message and suggest a time for a call.
  2. 2In 30 minutes we work out what has to change in your system.
  3. 3You get a fixed written quote — with no obligation.

Prefer email? Write to kontakt@fakturai.pl

RAEOLAS Richard Ndah

Pobiedziska, Poland

NIP 7773451872

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Knowledge

KSeF guides

Practical articles about KSeF 2.0.

FakturAI — KSeF 2.0 integration for companies with their own systems