The Tax Office will know everything about you – what does this mean for a Sole Proprietorship (JDG) with an A1 Certificate?

Imagine you have a camera in your office that runs 24/7 and transmits the image straight to the Tax Office. Except it’s not a camera, but a set of modern IT systems. You see a client in Belgium, you sign a contract, you issue an invoice in Euros, and before the client can even make the transfer, the Tax Office already knows:

• Who needs to pay
• How much
• What for
• When

What once required a controller’s visit and binders full of documents now happens automatically, without your knowledge or participation, in real-time—not just in Poland, but across the entire EU

In our accounting firm, we serve hundreds of entrepreneurs working abroad with the A1 Certificate. Recently, we have increasingly heard the same question: “Does the Tax Office really see all my transfers from Germany?”

The answer is: Yes. And with every year, they see more and more.

Understanding what the Tax Office sees will help you better prepare for potential audits.

October 2024 brought us a record number of requests for clarification for our A1 clients. Mr. Krzysztof, our long-time client running an electrical business with contracts in Belgium, received an inquiry concerning discrepancies between account inflows, invoices in the JPK VAT file, and data the Polish office received from the Belgian system. We had seven days to prepare a response.

That is why it is vital to know what the Tax Office sees in your documents and transactions.

“But I settle everything honestly,” he repeated, clearly stressed. And he was right. The problem is that in the era of digital tax control, “honestly” is not enough. You need to settle your accounts coherently—so that every zloty in your account matches every invoice, every invoice matches every transfer, and every transfer matches every entry in the system.

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Why Are These Changes Being Introduced?

The official reason is to tighten the tax system and combat VAT fraud. Poland—like other EU countries—loses billions of zloty annually due to the so-called “tax gap.”

According to the Ministry of Finance, the VAT gap in Poland fell from 13.5% in 2023 to approximately 6.9% in 2024, primarily due to new analytical tools like JPK VAT and STIR. Now the government is taking the next step:

• It wants access to full accounting data in real-time.,
• It plans the integration of this data with international systems.
• It will utilize artificial intelligence to flag irregularities.

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What Is Already Operational Today?

JPK VAT – Standard Audit File for Tax (SAF-T) for VAT

Since 2018, every VAT entrepreneur sends a monthly electronic record of sales and purchases. The Tax Office sees:

• Who you invoiced
• The amount
• The date
• The currency

 A1 Example: Ms. Anna, a Sole Proprietorship (JDG) with an A1 Certificate, issues an invoice for crane operator services in the Netherlands. The Tax Office in Poland sees this transaction before the client even manages to pay her.

VAT Example: Mr. Krzysztof runs a JDG with an A1 Certificate and performs welding services in the Netherlands. He issues an invoice for EUR 12,000. The JPK VAT file reaches the office even before the money is transferred to his account. A few weeks later, due to an exchange rate difference, 1 [The sentence is incomplete in the original Polish. I will complete it to convey the full meaning intended in the tax context, assuming the intended meaning was to show a bank transfer amount].

Source: JPK – Ministerstwo Finansów

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STIR – Information Technology System of the Clearing House

Why Was STIR Created?

STIR was created to monitor the financial flow of companies and detect suspicious transactions.

How Does STIR Work?

Every bank in Poland daily sends the National Revenue Administration (KAS) information about:

• All inflows and outflows from company accounts
• End-of-day balances
• Foreign transfers

Real-Life Examples

A1 Example: Ms. Elżbieta, a Sole Proprietorship (JDG) with an A1 Certificate, receives a transfer from Germany for EUR 15,000. In the JPK VAT file, the invoice was issued for EUR 14,900 because the client deducted a EUR 100 service fee. However, STIR sees a higher transfer than the invoice and may flag this for analysis. Without good documentation, unnecessary explanations begin.

A1 Example: Mr. Marek receives a transfer from Germany, but the invoice has not yet been included in the JPK… (The text is incomplete, but the intention is clear: STIR registers the inflow immediately, exposing the lag or absence of the matching invoice record.)

Source: STIR – Ministerstwo Finansów

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What’s Coming in 2026?

KSeF – National e-Invoicing System

Effective February 1, 2026, KSeF will become mandatory for all active VAT taxpayers, including sole proprietorships. This means that every invoice issued and received by an entrepreneur will have to pass through the system.

During one of our recent training sessions, a client running a cleaning company with contracts in Germany and the Netherlands asked: “Does that mean the office will see every single one of my invoices in real-time?”

The answer is: Yes. And what’s more, the office will not only see it but will immediately subject it to analysis. With KSeF:

• The Tax Office will receive all contractor details, amounts, dates, and a detailed description of the service.
• The invoice will reach the central database of the Ministry of Finance the moment it is issued.
• Algorithms will compare this data with other registers and reports, detecting discrepancies almost instantly.

A1 Example: A Sole Proprietorship (JDG) with an A1 Certificate issues an invoice with the description “consulting services” for a client in Belgium, even though the work was actually for structural assembly. Such a description may be considered too general, and the transaction flagged for detailed analysis.

What the Tax Office sees can become a critical factor in running your business at any moment.

What to Do Today?

Introduce precise, factual descriptions of services on your invoices and establish with your accountant what wording is safe from a tax perspective in the context of KSeF and foreign business operations.

Source: KSeF – Ministerstwo Finansów

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JPK CIT and Other Reports – Why Sole Proprietorships (JDG) Will Also Be “On the Radar”

The obligation to report in the JPK CIT format starting in 2025 formally applies exclusively to corporate income tax payers (companies). The implementation schedule is divided into three stages:

• From January 1, 2025 – Companies with revenues exceeding EUR 50 million and tax capital groups.
• From January 1, 2026 – Other companies already filing JPK VAT.
• From January 1, 2027 – All other companies subject to CIT.

Source: Ministerstwo Finansów – struktury JPK w podatkach dochodowych

At first glance, Sole Proprietorships (JDG) might breathe a sigh of relief—this obligation formally does not concern them. But that’s only half the story.

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Why JDG Data Will Still Enter the System?

Companies subject to JPK CIT must report detailed information about their transactions, including:

• The Tax Identification Number (NIP) of the contractor (including Polish Sole Proprietorships/JDG).
• Date and number of the invoice.
• The KSeF e-invoice number, if it was issued electronically.
• Value of the transaction.
• Description of the transaction subject.

This means that if you are a JDG and issue an invoice to a company subject to JPK CIT, all this information will reach the Ministry of Finance’s database through your contractor.

Add to this the fact that a large proportion of companies will be operating in KSeF starting in 2026—and KSeF and JPK CIT will be integrated with each other—and we have a situation where a JDG’s invoices will enter the Tax Office system even without a mandatory reporting obligation on the JDG’s side.

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Real-Life Example

You must be aware of what the Tax Office sees to avoid future problems.

Mr. Michał runs a Sole Proprietorship (JDG) with an A1 Certificate and provides transport services for a large construction company in Poland. Starting in 2026, the company reports its ledgers via JPK CIT and uses KSeF.

In practice, this is what happens:

1. Michał issues an invoice via KSeF (because he is a VAT payer and is required to from February 2026).
2. The company records the invoice in its ledgers, which it reports via JPK CIT.
3. In the Ministry of Finance’s database, the data merges: Michał’s invoice from KSeF + the company’s detailed bookkeeping entries in JPK CIT + the bank transfer visible in STIR.

What does the Tax Office see in such a case? The Tax Office sees the full picture of the transaction—without the need to ask Mr. Michał for any documents.

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What the Tax Office Sees:

• The Tax Office can easily compare your invoices with account inflows (STIR) and with data from your contractors (JPK CIT).
• Errors in service descriptions, dates inconsistent with actual performance, or discrepancies in amounts will be visible immediately.
• Even if a Sole Proprietorship (JDG) is not formally subject to JPK CIT, the transaction’s “visibility” is complete thanks to the contractors who are subject to reporting.

Conclusion: It does not matter today whether you are in the group of entities obligated to use JPK CIT or KSeF—if you work for larger companies, you are already visible to the system.

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European Information Exchange Systems – Poland Does Not Operate in a Vacuum

Your tax and financial data can be transferred to Poland from abroad through several mechanisms:

Already Operational:

• CRS (Common Reporting Standard) – Automatic exchange of information regarding bank accounts between countries.
• DAC6 – Mandatory reporting of tax schemes.
• VIES – System for verifying VAT numbers within the EU.
• EESSI – Exchange of information regarding social insurance (important for A1).

Planned/Under Development:

• DAC8 – obejmie m.in. kryptowaluty i platformy online.
• Integration of KSeF with e-invoicing systems across the EU.
• Advanced analytical tools for linking bank, tax, and customs data

Source: EESSI – Komisja Europejska

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EESSI – The System That Tracks Your A1

May 2023 – When ZUS Started ‘Talking’ to Europe

One of our clients, who runs a hair salon and supplemented her income in Germany with an A1 Certificate, received a letter from the German authority regarding a discrepancy in EESSI data. The system detected that some invoices were issued to companies in different regions (Länder) than the one specified on the A1.

Thanks to our experience, we quickly helped the client clarify that these were sporadic, emergency trips that were appropriately documented.

How to Manage A1 in the EESSI Era

Do not forget what the Tax Office sees, as it can affect your settlements.

Precise Tracking of Working Days: You must maintain accurate records of work locations for every client under the A1 Certificate.

That is precisely why what the Tax Office sees is crucial in all your settlements.

Coordination with ZUS: You must regularly verify the status of your A1 and report any changes.

Documentation of Business Trips: It is necessary to archive tickets, hotel invoices, and confirmation of presence.

Example: Our IT consultant client worked remotely from Poland for a company in Ireland, but flew once a month for meetings. The Irish authority questioned the place of work. With our help, the client documented (including VPN logs, tickets, and schedules) that 90% of their work was performed from Poland. Holding an A1 Certificate means settling accounts in Poland despite providing services in another EU country. This requires full coherence across:

1. Invoices (KSeF, JPK VAT)
2. Account Inflows (STIR, CRS)
3. Social Insurance Data (EESSI)

Example 1: You work in Belgium for 8 months, issue invoices in Euros, and the inflows are in PLN. If exchange rate differences are not correctly described, the system will detect it.

Example 2: You only have foreign invoices but pay a low health contribution—the algorithm will notice that.

Do not forget what the Tax Office sees, as your actions could lead to severe penalties.

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10 Warning Signs That You Need Professional Help

Our experience shows that entrepreneurs with the A1 Certificate often seek help too late. Here are the warning signs:

1. You receive requests for clarification – even if you can answer, it’s a sign that something is wrong.
2. You have accounts in several countries – CRS (Common Reporting Standard) transmits all data; you need to report it coherently.
3. Your revenues are irregular – STIR algorithms look for anomalies.
4. You issue invoices in different currencies – every exchange rate difference is a potential alert.
5. You work for contractors from various countries – EESSI (social insurance exchange system) shares information between countries.
6. You don’t understand all the systems – JPK, STIR, KSeF, CRS are just the beginning.
7. You fear an audit – fear means you lack certainty about your settlements.
8. You are wasting time on formalities – instead of growing your business, you are battling systems.
9. You have to track increasingly complicated regulations to understand what the Tax Office sees.
10. You want to sleep soundly – the certainty that everything is in order is priceless.

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Why You Need an Accountant Experienced in Foreign Income and A1 Certificate Settlements

New systems mean:

• No time to “rescue the situation” after an audit.
• Errors detected immediately.
• Full data analysis by AI.

A good accountant will:

• Understand the specifics of A1 Certificates.
• Know Polish taxes and understand those applicable in EU countries.
• Ensure correct invoice descriptions in KSeF.
• Monitor data coherence between all systems.
• Prepare you to operate in a real-time audit environment.

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Summary – Prepare Now

The Tax Office will have access to your data 24/7.

Data from Poland and the EU will be analyzed in real-time.

Sole Proprietorships (JDG) with the A1 Certificate must have flawless and coherent settlements.

Contact us – we will prepare your company for KSeF, JPK, STIR, and the new audits.