How much does Aplikacja Podatnika KSeF cost?

Nothing. The app is free — no subscription, no invoice cap, no premium tier. The Ministry of Finance publishes it as the baseline tool for mandatory KSeF.

How do I log in to Aplikacja Podatnika KSeF?

Go to ap.ksef.mf.gov.pl and confirm your identity with Profil Zaufany, a qualified signature, a qualified seal or a KSeF certificate. For a small business the shortest route is Profil Zaufany, because you most likely already have one.

Can I issue a correction invoice in the free app?

Yes. The app handles invoices and correction invoices in the FA(3) structure, plus VAT RR invoices and their corrections in the FA_RR(1) structure.

How does Aplikacja Podatnika differ from e-mikrofirma?

Aplikacja Podatnika is a KSeF client: it issues, receives and searches invoices and manages permissions. E-mikrofirma lives inside e-Urząd Skarbowy and goes one step further into bookkeeping, moving invoices received from KSeF straight into your VAT records. You log in to it through login.gov.pl or the mObywatel app.

When does the free app stop being enough?

When invoices are created without you. At a dozen or so invoices a month typed by hand, the app is a good choice. If sales run themselves and the invoice already exists in another system before you open the browser, retyping it into a form is work nobody has to do.

Aplikacja Podatnika KSeF: the Ministry of Finance's free app

Q: What is Aplikacja Podatnika KSeF?

It is the Ministry of Finance's free browser application. You can issue invoices in KSeF, receive invoices from suppliers, download UPO confirmations and grant access to employees and your accountant. It runs at ap.ksef.mf.gov.pl and installs nothing on your computer.

Aplikacja Podatnika KSeF is the Ministry of Finance's free browser application at https://ap.ksef.mf.gov.pl. You can issue invoices in the FA(3) structure, receive invoices from suppliers, download UPO confirmations and grant permissions. It costs nothing, installs nothing, and at a dozen or so invoices a month it genuinely is enough.

Since 1 February 2026 the largest taxpayers issue invoices in KSeF, and since 1 April 2026 everyone else does too. Receiving invoices through the system has been required since February, whatever the size of your business. So almost every business owner starts with the same question: what is this going to cost me? Possibly nothing, because the Ministry of Finance shipped its own complete tool.

What Aplikacja Podatnika KSeF actually is

It is a browser application built by the Ministry of Finance as an alternative to commercial software integrated with the KSeF 2.0 API. You do not install it. You open the address, log in and work on invoices.

Its users include taxpayers, public finance sector units and VAT group members, so the feature set is broader than a typical small business needs. You will not hit a wall where the "free version" ends, because there is no paid version.

There are three addresses, one per KSeF environment:

Production: https://ap.ksef.mf.gov.pl. Invoices here have legal effect.
TEST: https://ap-test.ksef.mf.gov.pl. Fictional identity, data with no legal meaning.
DEMO: https://ap-demo.ksef.mf.gov.pl. A real NIP and real login, but still a non-production environment.

If you have been looking for the app at older KSeF 1.0 addresses, it is not there. Those hosts are switched off, and plenty of Polish articles still point at them. We laid out the differences between environments in the guide on the KSeF test environment.

What it costs

Nothing. No subscription, no invoice cap, no extended package. A mandatory system does not mean a mandatory expense: a business issuing a few invoices a month can get through the entire KSeF obligation without paying anyone a złoty.

How to log in

KSeF accepts five ways of confirming your identity. Four of them open the app in a browser; the fifth is for software.

Profil Zaufany. The shortest route for a small business or sole proprietorship, because almost everyone who has filed a PIT online or done anything through mObywatel already has one. Nothing to buy, nothing to order, and you log in exactly as you do to e-Urząd Skarbowy.

Qualified signature. If you already have one, it works straight away. Buying one purely to get into KSeF makes no sense when Profil Zaufany is free.

Qualified seal. For companies and institutions that sign documents with a company seal rather than a named person's signature.

KSeF certificate. The system issues it itself, once you have logged in with one of the methods above. There are two kinds: one for authentication, the other for marking invoices in the offline modes. If you plan to issue invoices outside the system in offline24 mode, you need the second kind.

KSeF token. This is a method for software, not for a human clicking in a browser. It comes with two catches. First, tokens are only available until 31 December 2026. Second, a session authenticated with a token cannot request a certificate, so if you start with a token you will still come back for the certificate with Profil Zaufany or a signature. We compare the two in the guide on tokens and certificates.

After logging in you pick the entity you are acting for. The owner of a sole proprietorship holds owner permissions automatically and grants themselves nothing. In a company, somebody authorised has to hand them out first.

It takes a quarter of an hour, so there is no point putting it off.

Go to https://ap.ksef.mf.gov.pl and choose Profil Zaufany. If you log in to e-Urząd Skarbowy, you already know this step.
Pick the entity. A sole proprietorship picks its own NIP. If you work for several companies or run an accounting office, you will see the list of entities somebody has given you access to.
Look at purchase invoices first. It is the quickest way to check you are looking at the right company, and it pays off immediately: your suppliers' invoices are already there.
Hand out permissions. Your accountant or accounting office needs their own access. You grant it against a NIP or PESEL, so nobody has to log in with your Profil Zaufany.
Generate a certificate, but only if software is going to send your invoices or you plan to issue them offline. Clicking in the browser needs no certificate.

Outages and no internet

You do not stop issuing invoices when your signal drops or KSeF stops answering. The regulations provide special modes: offline24, an offline mode for announced system unavailability, an emergency mode, and a total failure under which invoices are issued outside the system altogether. The deadline for sending the invoice to KSeF depends on which mode applied.

Two of these matter to a user of the free app. Invoices issued offline and sent later show up in the app like any other. And marking invoices in the offline modes needs the second kind of KSeF certificate, so if you expect to invoice without internet one day, get it in advance rather than on the day of the outage.

What you can do in the app

The feature list is long for a tool nobody pays for.

Issuing invoices. Invoices and correction invoices in the FA(3) structure, the current schema. It also handles VAT RR invoices and their corrections in the FA_RR(1) structure, which matters when you trade with flat-rate farmers. You fill in a form, confirm, and the document goes to KSeF.

Receiving invoices. Supplier invoices sit in one place instead of being clicked out of each vendor's portal separately. For many small businesses this is the single biggest benefit of KSeF as a whole, and you get it for free. It is also why an account is worth having even for a business that does not yet have to issue invoices in KSeF: receiving started for everyone on 1 February 2026 and your suppliers are already filing there. We cover the deadlines in the guide on mandatory KSeF.

Searching and downloading. You browse documents, filter them and download them as XML or PDF. The app also shows invoices issued offline and sent to KSeF later, along with PEF invoices from the public procurement platform.

Downloading UPO. You can pull the receipt confirmation for a single invoice or for many at once. That matters for archiving, because UPO is the proof that the invoice was genuinely issued.

Managing permissions. You grant and revoke access for an accountant, an employee or an accounting office. The app also handles subordinate units, VAT group members and the composite identifiers used for EU-model self-invoicing.

Certificates and tokens. You file and collect certificate requests in the app. Tokens can be generated and revoked here until the end of 2026.

QR codes and anonymous access. The app handles the verifying QR codes a buyer uses to check an invoice without logging in. We describe them in the guide on the QR code on an invoice.

Session history. You can see who connected to the system on behalf of your company, and when.

There is also a KSeF mobile app. It issues invoices and corrections from your phone, stores a list of buyers and bank accounts, and finds and downloads earlier documents. You confirm your identity once, through mObywatel, mojeID, e-dowód or Profil Zaufany, and then log in with biometrics or a PIN.

Aplikacja Podatnika vs e-mikrofirma

These are two different tools from the same ministry, and they are easy to confuse.

Aplikacja Podatnika KSeF is a KSeF client. It issues, receives, searches and manages permissions. It stops at the boundary of the system and does not look into your bookkeeping.

E-mikrofirma lives inside e-Urząd Skarbowy and goes one step further. Besides issuing invoices in KSeF, it can move invoices received from KSeF straight into your VAT records without retyping the data. You log in through login.gov.pl or the mObywatel app. Tax credentials will not get you in.

Short version: if you are looking for an invoicing tool, go to Aplikacja Podatnika. If you want the same place to keep your VAT records, look at e-mikrofirma.

Before your first production invoice

Every invoice sent to KSeF in production is a document in legal circulation. There is no undo button, because KSeF has no concept of cancelling an invoice. Mistakes are fixed with a correction.

So practise the first time in the test environment. On TEST the authorisation is fictional, so you log in with a made-up NIP and cannot break anything. You will see what the form looks like, what a KSeF number looks like and where UPO is downloaded from, before any of it counts. On DEMO you can check the same thing with a real login and real permissions, still with no legal effect.

What the app does not do

Three things, and none of them is a flaw. They are simply the limits of the tool.

You fill in each invoice by hand. You open the form, type the buyer, the line items, the rates, the dates, and confirm. The app helps, but it does not know your sales, so the data has to come off the keyboard.

There is no connection to your sales system. The app cannot see your shop, your payment gateway or your subscription system. Nothing in it will catch a new transaction and turn it into an invoice.

There is no bulk automation. One invoice means one pass through the form. At two invoices a day that is trivial; at twenty it becomes a job.

Where the line runs

For some businesses this tool is enough forever; for others it stops being enough after a few months. The line runs in a specific place.

The free app is the right answer when a human issues the invoice. A law firm invoicing ten clients once a month. A construction business invoicing when a job ends. A freelancer with three regular clients. A shop that mostly sells to consumers and issues a business invoice now and then. In all of those, somebody sits down anyway, decides what goes on the invoice and types it in. Typing it into the Ministry of Finance's form takes exactly as long as typing it into a paid program. Given that, there is no reason to pay. We go into it further in the guide on KSeF for sole proprietorships.

It stops being the right answer when the invoice is created without you. A subscription shop where a dozen plans renew every morning. A SaaS app that charges cards on the purchase anniversary, so invoices land on every day of the month. Sales through Stripe, where the document is already finished, with a number, an amount, a currency and the buyer's details, before you even open a browser.

In a business like that, retyping is not merely tedious. It is a tool of the wrong shape. The invoice already exists as data, and the form makes a human turn it back into clicking. At twenty invoices a day that becomes an hour of work every day and a daily chance of a typo in a NIP that comes back as a correction.

So the line does not run at some number of invoices. It runs at one question: does a human create the invoice, or does a system create it and a human merely move it? If a human creates it, the free app is enough forever. If they are moving it, the moving should happen by itself.

Where KSeF Kit fits

This is a narrow case, and we say so plainly so nobody signs up who does not need to.

KSeF Kit only works with Stripe. It is not an invoicing program with a form where you type line items. It is a bridge between the invoices Stripe already issues and KSeF. If you invoice from a Polish accounting program, from a spreadsheet or by hand, we are not for you and you are better off with the free app.

If you do sell through Stripe, it works like this: you finalize an invoice in Stripe, we convert it to FA(3), file it to KSeF, and the KSeF number and UPO come back onto that same Stripe invoice. Nobody retypes anything.

The free plan is 6 accepted invoices per rolling month, no card, in production and with full features including corrections. Paid plans raise only the limit: 9 zł for 75 invoices, 49 zł for 250 and 129 zł for 1500 a month.

And one sentence we will not take back: if you issue a few invoices a month and you do it by hand, stay with Aplikacja Podatnika. It is free, it is official, and it does everything you need. See how filing from Stripe works if your sales really do run themselves.