How should sole traders and freelancers prepare for KSeF?

Most KSeF guides were written for companies with an accounting department. A freelancer issuing six invoices a month has a different problem: not understanding the whole system, just knowing exactly what to do to stay out of trouble.

This matters right now (as of 8 October 2026) because the PLN 10,000 threshold expires on 1 January 2027. Under the current act, penalties under Article 106ni of the Polish VAT Act apply from 1 January 2027. On 16 September 2026 the Ministry of Finance announced it will move them to 1 January 2028; that is a bill not yet passed, and it moves only the penalties, not the obligation to use KSeF. It is worth setting this up calmly now instead of scrambling over the New Year weekend.

Here is the minimum: six things a JDG (Polish sole proprietorship) actually has to handle, and nothing beyond that.

1. Work out which scenario you are in

The timeline is simple but has three layers. Per the Ministry of Finance guidance for sole traders and SMEs:

• From 1 February 2026, issuing through KSeF became mandatory for businesses with 2024 sales above PLN 200 million including VAT. That is not you, but their invoices already reach you through the system.

• From 1 February 2026, everyone must receive invoices through KSeF. Legal form and size are irrelevant.

• From 1 April 2026, issuing became mandatory for everyone else, including sole traders and VAT-exempt taxpayers. The smallest ones, who fit within the PLN 10,000 gross monthly threshold (point 2), join only on 1 January 2027.

Receiving is the part people forget. The Ministry states plainly that KSeF sends no notifications: your software, or you manually, must poll the system for new documents. A supplier invoice you never downloaded does not stop existing. It simply never enters your deductible costs.

2. The PLN 10,000 threshold: who can actually use it

A transitional provision allows invoices to be issued on paper or electronically outside KSeF until 31 December 2026, as long as the combined monthly value of sales documented by such invoices does not exceed PLN 10,000 gross.

Three points that rarely get stated loudly enough:

Only KSeF-mandatory invoices count towards the threshold. Consumer invoices, cash-register receipts with a buyer NIP (Polish tax ID) up to PLN 450 treated as simplified invoices, and cases excluded by regulation under Article 106s of the VAT Act stay out of the pool. In practice the threshold covers plain B2B sales.

The calendar month and the invoice issue date decide, not the sale date and not the payment date.

Crossing it is irreversible. The obligation kicks in from the specific invoice that pushed you past PLN 10,000. Later months with PLN 3,000 in sales change nothing. This is not a monthly allowance, it is a single-use ticket.

Example: a freelance designer issues three B2B invoices in October at PLN 2,800 gross each (PLN 8,400 total). On 27 October a fourth arrives, PLN 2,000. That fourth invoice must go through KSeF, and so must every invoice afterwards, permanently. A quiet November with PLN 4,000 in sales does not restore the right to send PDFs.

If your revenue hovers around PLN 10,000, relying on the threshold is a waiting game with the risk that you miss the moment. The simpler option is entering KSeF deliberately, at a time you choose, before a random invoice chooses for you.

3. Access: how you actually log in

There is no login and password for KSeF. The Ministry lists the available authentication methods: Trusted Signature via Profil Zaufany (Poland's national digital identity), a qualified electronic signature, a qualified electronic seal, a token, or a KSeF certificate. Since 14 February 2026 KSeF has been integrated with the National Node of Electronic Identification, so you log in to the Taxpayer Application through login.gov.pl: with the mObywatel app (QR code scan), mojeID (online banking), an e-ID card or Profil Zaufany. A qualified signature and seal still work as well. mObywatel is only for logging in, not for issuing invoices.

For a sole trader the practical path looks like this:

1. Log in for the first time with Profil Zaufany. As a natural person identified by NIP you hold owner permissions automatically.

2. Generate an Authentication-type KSeF certificate, which authenticates your invoicing software.

3. If you want offline mode to actually work, generate an Offline-type KSeF certificate as well (a different certificate from the one used to log in). Without it you cannot produce the second QR code (KOD II) required on an invoice handed to a buyer outside the system.

Certificates are free, issued by the Ministry's Certification Centre, valid for up to two years. Details: KSeF certificates on podatki.gov.pl.

What about tokens? Under the current rules KSeF tokens expire on 31 December 2026. At consultations on 9 June 2026 the Ministry of Finance proposed keeping them, but no regulation has been adopted yet, so moving to a KSeF certificate is the safer choice. A certificate works in every scenario, while a token cannot be used to obtain an Offline certificate: the first login that issues a certificate requires a qualified signature, a qualified seal or Profil Zaufany. If you want to decide once and never revisit it, choose the certificate. Biurko connects to KSeF with Profil Zaufany or a certificate, not with a token.

4. What actually changes in day-to-day invoicing

A B2B invoice is no longer a file you email. It is an XML document in the FA(3) schema, submitted to KSeF, to which the system assigns a number. Only at that point, in online mode, is the invoice issued in the legal sense; an invoice KSeF rejects has not been issued.

Practical consequences:

• No buyer acceptance needed. The invoice counts as received the moment KSeF assigns its number.

• Your own numbering stays yours. KSeF assigns its own identifier, but your invoice number (say 12/10/2026) is still yours to set.

• B2C invoices are optional. The same applies to invoices issued to a business owner buying for private purposes.

• Foreign clients get a visualisation. You issue the invoice in KSeF and pass it to the buyer in an agreed form, typically a PDF carrying a QR code.

• Archiving comes for free. Invoices sit in KSeF for 10 years. One of the few parts of this obligation that makes your life easier.

5. When KSeF is down

Four situations, different rules, deadlines counted in business days. Worth knowing, because confusing them can turn into a penalty once penalties apply.

An invoice issued offline carries QR code I marked OFFLINE; if you hand it to the buyer outside the system, it also needs QR code II marked CERTYFIKAT, generated from your Offline-type KSeF certificate. Full description of the modes: Ministry of Finance Q&A.

6. What lands on 1 January 2027

Three changes at once:

• The PLN 10,000 threshold disappears. All B2B invoices go through KSeF, with no value-based exemption.

• Administrative penalties under the current act. Under Article 106ni of the VAT Act, the head of the tax office may impose a penalty of up to 100% of the tax shown on an invoice issued outside KSeF, or up to 18.7% of the total amount due on an invoice with no tax shown. Under the current act, penalties apply to breaches committed from 1 January 2027. On 16 September 2026 the Ministry of Finance announced it will move them to 1 January 2028; that is a bill not yet passed, and it moves only the penalties, not the obligation to use KSeF.

• KSeF number in transfer titles. The new Article 108g of the VAT Act applies to payments made from 1 January 2027.

Checklist for this week

1. Check whether you are receiving KSeF invoices at all. If not, deductible costs are already slipping past you.

2. Add up your B2B sales for the last three months and see how close to PLN 10,000 you run.

3. Log into the KSeF Taxpayer Application with Profil Zaufany and confirm you can see your business.

4. Generate an Authentication-type KSeF certificate, and an Offline-type one as well if you work on site or on unreliable internet.

5. Settle with your accountant who issues invoices, you or the bureau. Grant permissions to the bureau as an entity rather than to individual staff.

6. To practise without legal effect, use the Biurko demo (demo.biurko.io, 7-day access, the KSeF demo environment). An account on app.biurko.io sends invoices to production KSeF, so every invoice you send there is real.

7. Put 1 December 2026 in the calendar as the date by which everything must run in production.

Summary

KSeF for a sole trader is not an implementation project. It is a handful of decisions: how you log in, what you issue with, who holds permissions, and what you do when the system does not answer. The rest happens in the background. The real risk is not the regulation, it is pushing those decisions to December.

Biurko is built around KSeF rather than bolted onto an accounting suite. Connection to KSeF with Profil Zaufany or a certificate (your own or one ordered through Biurko), FA(3) submission, purchase invoice import (automatic once enabled in company settings), and common KSeF errors translated into plain language. Create an account – every new company gets 14 days of the TEAM plan without a card, then moves to the free plan (FREE). To practise without legal effect, use the Biurko demo (demo.biurko.io, 7-day access, the KSeF demo environment); an account on app.biurko.io sends invoices to production KSeF, so every invoice you send there is real.

FAQ

When did KSeF become mandatory for sole traders in Poland? On 1 April 2026. The obligation covers all taxpayers except the largest companies, which entered on 1 February 2026, and the smallest ones, who join on 1 January 2027. Legal form does not matter and VAT-exempt taxpayers are included. The PLN 10,000 monthly threshold still applies until 31 December 2026.

How do I calculate the PLN 10,000 KSeF threshold? Add up the gross amounts of invoices issued in a given calendar month that would otherwise be mandatory in KSeF. Consumer invoices and receipts with a NIP treated as simplified invoices are excluded. The invoice issue date determines the month.

Can I go back to PDF invoices after crossing the threshold? No. You lose the right to invoice outside KSeF starting with the invoice that crossed PLN 10,000, and you do not regain it in later months, even with lower sales.

Do I need paid software for KSeF? No. The Ministry of Finance provides a free KSeF Taxpayer Application and a KSeF Mobile Application. Paid tools make sense when you need automation, accounting integration, multiple entities, or properly handled offline modes.

Do invoices to private customers go through KSeF? They do not have to. Issuing invoices to consumers, and to a business owner buying for private purposes, is voluntary in KSeF. Those invoices also stay outside the PLN 10,000 threshold.