KSeF 2027 for the smallest businesses: what to prepare in December

From 1 January 2027, the last transition period in KSeF (Krajowy System e-Faktur, Poland’s national e-invoicing system) comes to an end. Businesses that issued invoices for small amounts to other businesses in 2026 could still do it the old way: in a program, in a word processor or on paper. From the new year, every invoice for a business is created in KSeF, including in a sole proprietorship with a few invoices a month.

The good news: for a few invoices a month, you don’t need paid software, and getting ready will take one afternoon. Below I’ve gathered who the deadline applies to, what free tools the Ministry of Finance (Ministerstwo Finansów) provides and what to do in December so that you can issue your first invoice in January without stress. I describe the situation as of 30 October 2026, based on the websites of the Ministry of Finance and the Sejm (the lower house of Poland’s parliament). This is not tax advice: confirm your situation with your accountant.

Who the 1 January 2027 deadline applies to

Until the end of 2026, a transitional provision (Art. 145m of the ustawa o VAT, Poland’s VAT Act) allows invoices to be issued outside KSeF if the total gross value of sales documented with such invoices in a given month does not exceed PLN 10,000. From 1 January 2027, this exception disappears. The Ministry of Finance says plainly that from that day KSeF is mandatory for all businesses. This also applies to VAT-exempt businesses if they issue invoices to other businesses.

How to count the limit according to the explanations on the KSeF website:

• you count gross amounts, separately for each month, by the invoice issue date, not the date of sale,
• you include only invoices that would have to go to KSeF without this exception, which in practice means invoices for businesses,
• you don’t include invoices for private individuals, sales documented with a receipt alone, invoices from a cash register or receipts with a NIP (Polish tax ID) up to PLN 450.

Example: in November, an electrician issues three invoices to businesses for PLN 3,000 gross each and gives private customers receipts. That makes PLN 9,000, so they stay within the limit. If a fourth invoice to a business in the same month raises the total to PLN 12,000, that very invoice and all the following ones must be created in KSeF. A weaker December doesn’t undo anything: once you exceed the limit, you stay in KSeF.

What changes in January and what stays the same

The most important conclusion for a small business: you document sales to private individuals just as before. KSeF concerns invoices for businesses. Most invoices from your suppliers already go to KSeF today, so it’s worth checking it even if you don’t yet have to issue invoices there yourself.

Penalties: what is known as of 30 October 2026

Under the rules in force today, financial penalties for KSeF errors (Art. 106ni of the VAT Act) are to apply from 1 January 2027. On 20 October 2026, the government adopted a bill that moves them to 1 January 2028, as the Ministry of Finance announced. The bill went to the Sejm as print no. 3245 and passed its first reading on 21 October. On 30 October, the bill was before the Sejm’s Public Finance Committee (Komisja Finansów Publicznych) and was not yet law. The next Sejm sitting was scheduled for 5–6 November, so check what stage it has reached.

Two things are certain regardless of what happens to the bill:

• the obligation stays: the postponement concerns penalties, not KSeF itself,
• the tax office will react: in the bill’s explanatory memorandum, the government announces that tax offices will first remind businesses of the obligation, and may then check whether not using KSeF leads to unreliable VAT reporting.

That’s why I wouldn’t plan January around the idea that “there are no penalties anyway”. It’s better to get ready in December, when a mistake costs nothing.

Free tools from the Ministry of Finance

For a few invoices a month, the free apps are enough. On the KSeF website, the Ministry lists three:

1. Aplikacja Podatnika KSeF (KSeF Taxpayer Application, in the browser at ap.ksef.mf.gov.pl): issuing, receiving and viewing invoices and corrections, downloading them as XML and PDF, granting permissions, invoices from offline mode and QR codes. It also has a Demo version for practice.
2. The KSeF mobile app (Google Play and App Store): issuing invoices and corrections, a list of buyers and bank accounts, searching for invoices, offline mode. The first login is through login.gov.pl, then a PIN or biometrics.
3. e-mikrofirma in e-Urząd Skarbowy (the tax office’s online portal): issuing invoices in KSeF and receiving purchase invoices straight into your VAT records, without retyping. You log in through login.gov.pl or mObywatel (Poland’s official government app), not with tax data alone.

How to choose? If you invoice from your phone, out in the field, start with the mobile app. If you keep your VAT records yourself in e-Urząd Skarbowy, e-mikrofirma will be the most convenient. If you already have invoicing software or online accounting, ask the provider whether it sends invoices to KSeF. Then you only change the way you log in.

If your software connects to KSeF with a token, also ask about a KSeF certificate. On the Taxpayer Application page, the Ministry still states that tokens can be generated until 31 December 2026. In the KSeF questions and answers, however, it already writes that it is keeping tokens with no end date and will amend the regulation (rozporządzenie) to do so. Until that change, it’s better to have a backup.

A plan for November and December in 7 steps

1. Calculate the limit for recent months. Together with your accountant, check whether in 2026 your sales on invoices to businesses have already exceeded PLN 10,000 in any month. If so, KSeF already applies to you now, not from January.
2. Check that you can log in. In a sole proprietorship, you have owner permissions automatically, and you log in through login.gov.pl: mObywatel, online banking, e-dowód (electronic ID card) or Profil Zaufany (Trusted Profile, Poland’s free e-ID). A company without a qualified electronic seal files a ZAW-FA notification in e-Urząd Skarbowy or through e-Doręczenia (Poland’s official electronic delivery system; since 2026 not through ePUAP). If you don’t have an e-Doręczenia address yet, I describe it in the guide on the e-Doręczenia obligation.
3. Grant permissions. In the Taxpayer Application, give access to your accounting office and to the person who issues invoices. Don’t leave all your invoicing on one person’s phone.
4. Do a trial run in the Demo version. Issue an invoice, a correction and an invoice with two VAT rates. Demo works like the real system, but the invoices have no legal effect. The Ministry points out, however, that a business whose NIP appears on such an invoice, even a made-up one, may have access to its data. So don’t enter real customer data or confidential information in trial invoices.
5. Put your data in order. Enter your details and bank account number, and then your regular customers with the correct NIP and full name. This matters more than it used to: in KSeF, the buyer can no longer issue a corrective note (nota korygująca), so you fix every mistake with a corrective invoice.
6. Decide how the customer will get the invoice. A Polish business will find it in KSeF. To a customer outside KSeF, for example from abroad, you send a PDF, which must have a QR code with the KSeF number.
7. Prepare a plan B. Without internet, you can issue an invoice in offline24 mode and send it to KSeF no later than the next business day. In the case of an outage announced by the Ministry, you have 7 business days from its end. An offline invoice has a second QR code, which requires a KSeF certificate. You apply for it in the Taxpayer Application, so do it in December.

In December, also send a short message to your regular customers. You can copy it:

Hello, from 1 January 2027 we issue invoices in KSeF, Poland’s national e-invoicing system. You will find them in KSeF, and on request we will also send a PDF with a QR code. Please check whether we have your current company details: [name, NIP, address]. Thank you!

Website, form and store: what to fix while you’re at it

KSeF concerns invoices, but the data for invoices is often collected by your website. It’s worth reviewing a few places:

• Order or inquiry form: a separate field for the NIP and the full company name, with a simple check of the NIP length. Fewer typos mean fewer corrections.
• Online store: invoices for businesses go through KSeF, while receipts for private customers stay unchanged. I describe what to check in the plugin and how to test it in the guide KSeF for online stores.
• Information for customers: one sentence in your FAQ saying that you issue invoices for businesses in KSeF and send a PDF on request. It will save you questions in January.
• Retyping by hand: if you retype website orders into your invoicing software, this is a good moment for automation. You’ll find a comparison of tools for such flows in the guide Make, Zapier or n8n, and I can build a ready-made automation as part of process automation.

What not to do

• Don’t leave logging in until 31 December. The ZAW-FA notification and granting permissions take a while, and in the last days of the year you won’t be the only one doing it.
• Don’t issue an invoice to a business in a word processor “because the system is down”. That’s what offline mode is for.
• Don’t practice on real customer data. A trial invoice in the Demo version has no legal effect, but the business whose NIP appears on it may have access to it.
• Don’t count on there being no penalties. The postponement bill is not law yet, and the obligation stays anyway.

Summary

From 1 January 2027, every invoice for a business is created in KSeF, even in the smallest business. In November, calculate the limit and check your login, and in December, grant permissions and do a trial run in the Demo version. For a few invoices a month, the free Ministry of Finance apps are enough. Confirm the tax details with your accountant and the current rules in the KSeF questions and answers, because the rules may still change before the end of the year.

If your invoices are created from orders on your website or in your store, write to me. I’ll connect your form or online store with your invoicing software so that the data reaches KSeF without retyping. I reply within 24 hours, and new clients get 20% off their first order.