Evidence in Tax Proceedings

Evidence in Polish tax proceedings is anything that helps to clarify the case and is not contrary to law (Article 180(1) of the Tax Ordinance Act of 29 August 1997, the Tax Ordinance). The catalogue is open. The statute lists, by way of example, tax books, tax returns, witness testimony, expert opinions, inspections, tax information, documents from the analytical work of the National Revenue Administration, from verification activities and from tax and customs and fiscal audits, as well as materials from criminal and fiscal penal proceedings (Article 181).

It is the authority that gathers the evidence and must establish the facts in accordance with the truth (Articles 122(1) and 187(1)). Since 4 November 2025 it must resolve irresolvable doubts as to the facts, in proceedings initiated ex officio, in the party’s favour (Article 122(2)). The party has the right to take part in the taking of evidence, to file evidentiary motions and to comment on the whole file before a decision is issued.

In practice, most tax disputes are won or lost on the evidence, not on the interpretation of the statute. It therefore pays to know what the authority may use, what it must ensure and where the limits lie.

Key points

• Open catalogue: any means that serves to clarify the case and was not obtained contrary to law is admissible (Article 180(1)). The Tax Ordinance establishes no formal hierarchy of evidence. The authority assesses the credibility and weight of each item against the whole file (Article 191). Special rules apply nonetheless: reliable and non-defective books are proof of what they record (Article 193(1)), and an official document proves what was officially certified in it (Article 194(1)).
• The authority gathers evidence ex officio and considers it exhaustively (Articles 122(1) and 187(1)). A party’s request to take evidence must be granted if it concerns circumstances relevant to the case, unless they are already sufficiently established by other evidence (Article 188).
• Evaluation is free, but based on the whole file (Article 191). A fact may be treated as proven only if the party had the opportunity to comment on the evidence (Article 192). Before issuing a decision the authority sets the party, as a rule, a 7-day period to comment on the evidence gathered (Article 200(1)). Exceptions are listed in Article 200(2), and before a decision of the Head of the National Revenue Administration applying the general anti-avoidance rule the period is 14 days (Article 200(3)).
• Materials from criminal proceedings, including interview records and transcripts of lawful surveillance, may serve as evidence without repeating the acts (Article 181). The authority must, however, verify the lawfulness of their acquisition and use and allow the party a real opportunity to test them (Supreme Administrative Court judgments of 7 February 2019, I FSK 1860/17 and I FSK 1881/17; CJEU judgments in C-419/14 WebMindLicenses and C-189/18 Glencore).
• The party must be notified of the place and time of witness examinations, expert evidence or inspections at least 7 days in advance. It may take part in those acts and put questions (Article 190). Close relatives of the party may refuse to testify (Article 196(1)). The party itself is examined only with its consent (Article 199). Since 1 October 2026 an examination may be conducted remotely (Article 199b).
• Breach of the rules on evidence is a ground of appeal and of a complaint to the administrative court. The court sets the decision aside if the breach could have had a material effect on the outcome (Article 145(1)(1)(c) of the Act of 30 August 2002, Law on Proceedings before Administrative Courts).

Principles of the evidentiary procedure

The evidentiary stage is governed by the principle of objective truth. The authority takes all necessary steps to clarify the facts precisely (Article 122(1)). It must gather and exhaustively consider the entire body of evidence (Article 187(1)). Facts of common knowledge and facts known to the authority ex officio need no proof, but the latter must be communicated to the party (Article 187(3)).

The principle of active participation (Article 123(1)) runs through every stage. The party may inspect the file (Article 178), take part in evidentiary acts (Article 190(2)), file evidentiary motions (Article 188) and make a closing statement (Article 200). The authority may amend, supplement or revoke its ruling on the taking of evidence at any stage (Article 187(2)). It may not, however, disregard evidence offered by the party merely because it considers the case already decided against it.

Evaluation of evidence is free, not arbitrary. Article 191 requires the authority to assess, on the basis of the whole file, whether a given fact has been proven. A selective assessment that ignores evidence favourable to the party breaches that provision and Article 187(1). The reasoning of the decision must identify the facts treated as proven, the evidence relied on and the reasons for rejecting other evidence (Article 210(4)). Our article on defective judicial reasoning shows how such omissions are challenged.

Article 192 completes the picture: a fact may be treated as proven if the party was able to comment on the evidence. Material excluded from the file on public interest grounds (Article 179) cannot, as a rule, be used to establish facts to the party’s detriment, because the party cannot respond to it. The Supreme Administrative Court so held in I FSK 1860/17. The Court of Justice accepts restrictions on access justified by the general interest, but requires a legal basis, proportionality and a real opportunity for the taxpayer to defend itself and for the court to review (judgment in C-189/18 Glencore). The course of proceedings is described in the entry on tax proceedings in Poland.

Burden of proof in a Polish tax case

The Tax Ordinance contains no general rule on the allocation of the burden of proof comparable to Article 6 of the Civil Code. Articles 122(1) and 187(1) place on the authority the duty to prove the facts from which it derives a tax liability: the existence of income, the understatement of the tax base, the fictitious nature of a transaction.

Case law has developed an auxiliary rule. A taxpayer who relies on facts producing a favourable result (a cost, the right to deduct VAT, a relief, an exemption) should hold the evidence and produce it. The taxpayer knows the circumstances and keeps the documents. The authority, for its part, may not replace proof with supposition or shift onto the party the burden of proving negative facts.

Two rules govern doubts. Article 2a concerns doubts about the content of tax provisions and requires them to be resolved in the taxpayer’s favour (see the entry on the principle of in dubio pro tributario). Article 122(2), added by the Act of 12 September 2025 and in force since 4 November 2025, concerns doubts about the facts. In proceedings initiated ex officio, irresolvable doubts as to the facts are resolved in the party’s favour.

The rule of Article 122(2) has three exceptions. It does not apply where the proceedings involve parties with conflicting interests or the outcome directly affects the interests of other persons. It does not apply where the law requires the party to prove specified facts. It does not apply where an important public interest, including a significant interest of the State, so requires. The rule therefore operates only after the evidentiary possibilities have been exhausted, not instead of them.

The legislature departs from the general model expressly in few cases. The furthest-reaching is Article 25g(1) of the PIT Act: in undisclosed income cases it is the taxpayer who demonstrates the income that covered an expense, save for data known to the authority ex officio (see the entry on undisclosed sources of income). Article 122(2) does not operate there. Another case is Article 193: reliable and non-defective books enjoy a presumption of conformity with reality. The authority must rebut it in a protocol of examination of the books (Article 193(6)), to which the party may file objections within 14 days (Article 193(8)).

Catalogue of evidence

Electronic data now dominates evidentiary practice. The authority may demand books and accounting records in the Standard Audit File structure (Article 193a). Since the mandatory National e-Invoicing System took effect in 2026 (1 February 2026 for the largest taxpayers, 1 April 2026 for the rest), it holds the content of structured invoices without any request. Discrepancies between a taxpayer’s SAF-T files and the data of its counterparties are today a typical trigger of an audit. Verification at the other party to a transaction is described in the entry on cross-checks at counterparties, and the limits on access to account data in our article on when the tax authority may inspect your bank account.

Criminal case files and surveillance material

Article 181 allows materials gathered in criminal and fiscal penal proceedings to be used. The courts accept that the Tax Ordinance does not adopt a principle of immediacy. The authority need not repeat interviews conducted by a prosecutor. It may add the records to the file and base findings on them. Three rules set the limits.

First, the party must be able to respond to the records added to the file (Articles 123(1) and 192). If it moves for a witness to be re-examined so that it can put questions, refusal is permissible only where the fact is already sufficiently established (Article 188).

Second, the authority enjoys no presumption that materials handed over by prosecutors or security services were lawfully obtained. In judgments of 7 February 2019 (I FSK 1860/17 and I FSK 1881/17) the Supreme Administrative Court held, following the Court of Justice’s judgments in C-419/14 WebMindLicenses and C-310/16 Dzivev, that the authority must examine whether operational surveillance was permissible in the case and conducted under court supervision. To base findings on transcripts, it should hold the recordings and allow them to be listened to. See our article on the exclusionary rule and wiretap evidence in tax proceedings.

Third, in the judgment of 16 October 2019 in C-189/18 Glencore the Court held that the authority may in principle be bound by findings made in proceedings against the taxpayer’s suppliers. The conditions are that the taxpayer has access to the evidence, can effectively challenge it, and the court can review the lawfulness of its acquisition and use. Being bound without those guarantees infringes the rights of the defence. The order of 12 November 2025 in C-475/24 Fashion TV RO and Maestro confirms that a tax court may examine evidence from criminal proceedings, even ones discontinued against persons other than the taxpayer, provided equality of arms and the rights of the defence are respected.

Evidence obtained contrary to law is a separate question, for example a recording made without the required court order or a document seized in an unlawful search. Article 180(1) excludes such evidence. The scope of the exclusion is discussed in the entry on admissibility of illegally obtained evidence and in our article on the fruit of the poisonous tree doctrine.

Witnesses, experts and the party

A person unable to perceive or communicate perceptions may not be a witness. Nor may a person bound by secrecy of classified information, as to matters covered by that secrecy, unless duly released from it. Nor may a clergyman as to facts covered by the secrecy of confession (Article 195).

The party’s spouse, ascendants, descendants, siblings, relatives by marriage in the first degree and persons in a relationship of adoption, guardianship or curatorship may refuse to testify. Any witness may decline to answer a question that would expose the witness or close relatives to criminal or fiscal penal liability or breach professional secrecy (Article 196(1) and (2)). Before the examination the authority warns the witness of these rights and of criminal liability for false testimony (Article 196(3)). The absence of the required warning is a procedural defect that may deprive the testimony of evidentiary value and must always be assessed in terms of the witness’s rights.

Since 1 October 2026 a party or witness may be examined remotely, with simultaneous direct transmission of image and sound, where the authority has the appropriate technical means. The examination may be recorded in image and sound or sound alone (Article 199b, added by the Act of 29 May 2026, Journal of Laws 2026, item 846). This does not displace the duty to notify the party and allow it to put questions.

An expert is appointed where specialist knowledge is required (Article 197(1)), and ex officio where tax law requires an opinion (Article 197(3)), for example when valuing real estate whose declared value departs from the market. The authority may not substitute its own assessment for an expert’s on specialist matters. A private opinion filed by the party is documentary evidence that must be considered. The party is entitled to respond to the expert’s opinion, although the notice under Article 190 concerns the place and time of the taking of evidence, not the drafting of a written opinion.

The party may be examined only with its consent (Article 199). Refusal carries no adverse inference. A demand to produce documents (Article 189) works differently: non-compliance allows the authority to decide on the remaining evidence. Refusal to testify does not remove the risk where the statute places the burden of proof on the taxpayer, as in undisclosed income cases. There, the absence of proof that an expense was covered counts against the taxpayer regardless of whether it testified. The standards for gathering the file are analysed in our article on evidentiary standards and the duty to gather evidence in Polish tax proceedings.

Determining the content of legal acts

The authority determines the content of a legal act according to the concurrent intention of the parties and the purpose of the act, not merely the literal wording of the declarations (Article 199a(1)). Where one act was performed under the guise of another, the tax consequences follow the hidden act (Article 199a(2)).

Where the evidence leaves doubt as to the existence of a legal relationship, the authority must apply to a civil court for a declaration (Article 199a(3)). The courts require objective doubts that ordinary evaluation of evidence does not remove. The provision is not a basis for disregarding genuine acts merely because they are unfavourable to the Treasury; that is the domain of the general anti-avoidance rule. The distinction between fictitious, sham and artificial transactions is explained in the entry on fictitious transactions.

What to check in the case file

• Whether the file contains every document relied on in the reasoning of the decision and whether the party had access to it. Where material was excluded under Article 179: whether the restriction had a statutory basis and proper justification, and whether a real opportunity to defend oneself and judicial review were preserved.
• Whether the party was notified of examinations and inspections 7 days in advance (Article 190(1)) and whether witnesses were warned of the right to refuse testimony (Article 196(3)).
• Whether evidentiary motions were decided by a reasoned ruling. Silent omission of a motion breaches Article 188.
• Whether criminal case records concern this case and whether the authority examined the lawfulness of surveillance material. A motion to re-examine a witness should be filed with a list of questions.
• Whether the period under Article 200 was set after the last evidentiary act, not before it, and whether any exception in Article 200(2) applies.
• Whether the authority resolved irresolvable factual doubts in the party’s favour (Article 122(2)) and, if it refused, whether it identified which exception it applied.
• Whether the reasoning addresses the evidence favourable to the party (Articles 191 and 210(4)). Omission of such evidence is a ground that often succeeds before the courts, as our article on the principle of free evaluation of evidence The route to court is described in the entry on appeals to administrative courts.

What legal assistance looks like in such a case

Counsel in a tax case works first of all on the file. It checks whether the authority’s findings rest on evidence the party has seen and could challenge, whether evidentiary motions were decided, and whether records from other proceedings concern this very case. That review produces the list of grounds for the appeal and the court complaint.

What the party itself contributes matters just as much. Documents, witnesses and private opinions filed before the decision become part of the material the court later reviews. Filed for the first time with the complaint, they rarely change the result, because the administrative court examines whether the authority correctly assessed what it had in the file. Counsel therefore builds the evidence at the stage of the proceedings before the authority, not only before the court.

Skarbiec Law Firm represents taxpayers in tax proceedings, tax audits and customs and fiscal audits and before the administrative courts, including cases built on material from criminal proceedings or from audits of counterparties.

Counterparts in other jurisdictions

The German Abgabenordnung builds the procedure on the inquisitorial principle (section 88 AO), balanced by the taxpayer’s duties of cooperation (section 90 AO), which are heightened in cases with a foreign element. In the United States the burden of proof in a dispute with the IRS rests as a rule on the taxpayer. It shifts to the administration only when the conditions of IRC section 7491 are met, including the production of credible evidence and the keeping of records. The Polish model is closer to the German one: the authority is responsible for establishing the truth and the party for producing evidence of facts in its favour. Its weakness remains the use of materials from criminal proceedings without the guarantees of a criminal trial.

Frequently asked questions

What can serve as evidence in Polish tax proceedings?

Anything that may contribute to clarifying the case and is not contrary to law (Article 180(1) Tax Ordinance): books, documents, witness testimony, expert opinions, inspections, SAF-T files, KSeF data, materials from other proceedings. The list in Article 181 is illustrative.

Who bears the burden of proof in a Polish tax case?

The authority must gather and consider the whole file and prove the facts from which it derives a tax liability (Articles 122(1) and 187(1)). It resolves irresolvable factual doubts in proceedings initiated ex officio in the party’s favour (Article 122(2)). The taxpayer should produce evidence of facts from which it derives a benefit, such as a cost or a deduction. A statutory reversal of the burden applies to income from undisclosed sources (Article 25g PIT Act).

Can the authority base a decision on records from criminal proceedings?

Yes, Article 181 permits it. The party must, however, be able to comment on that evidence (Article 192). The authority should examine the lawfulness of surveillance material and grant a motion to re-examine a witness unless the fact is sufficiently established by other evidence.

Do I have to testify in my own tax case?

No. The party is examined only with its consent (Article 199) and refusal is not evidence against it. A demand to produce documents (Article 189) is different: non-compliance allows the authority to decide on the remaining evidence.

Can family members refuse to testify?

Yes. The spouse, ascendants, descendants, siblings, relatives by marriage in the first degree and persons in a relationship of adoption, guardianship or curatorship may refuse (Article 196(1)). Any witness may decline a question that would expose him or her to criminal or fiscal penal liability (Article 196(2)).

How long does the party have to comment on the evidence?

As a rule 7 days, set by the authority before issuing the decision (Article 200(1)), and 14 days before a decision of the Head of the National Revenue Administration applying the general anti-avoidance rule (Article 200(3)). Omitting this step outside the exceptions in Article 200(2), or gathering new evidence afterwards without a new period, is a procedural breach.

Related entries

• Tax proceedings in Poland
• Admissibility of illegally obtained evidence
• Cross-checks at counterparties
• Tax decision
• Appeal from a tax decision to the court
• Unreliable books
• Fictitious transactions
• Tax audit protocol

Legal status as of 1 November 2026.

Publications by Skarbiec Law Firm Related to Evidentiary Proceedings in Tax Matters

The Exclusionary Rule in Tax Proceedings: Judicial Scrutiny of Wiretap Evidence

Evidentiary Standards and the Duty to Gather Evidence in Polish Tax Proceedings

The Principle of Free Evaluation of Evidence in Tax Proceedings

Robert Nogacki

Robert Nogacki is a Polish attorney at law (radca prawny), the founder and managing partner of Kancelaria Prawna Skarbiec (Skarbiec Law Firm), which has operated continuously since 2006.

The law is equal for everyone, but the parties rarely are: on one side stands an organization with time, money, and lawyers, on the other a person with one business, one nest egg, and one life.

Clients rarely come to him with a legal problem. They come with a problem that also has a legal side: an audit that began with a single invoice, money entrusted to someone who has disappeared, a company that has to be passed on before it is too late. Most such matters are decided long before the first letter is written, in decisions made without asking and in deadlines nobody remembered. So he begins by asking how the client got here, not what the client should have done.

He advises entrepreneurs and families from more than a dozen countries, including those whose accounts the tax office has just seized and who do not know what to do tomorrow morning. He defends them in tax audits, customs and fiscal inspections, disputes with the tax authorities, and criminal tax proceedings. He represents victims of investment fraud and Ponzi schemes. He helps families set up family foundations and plan succession, so that a life’s work outlasts a single generation.

Not every case can be won. Every case can be run so that the client knows where they stand. Since 2006 he has represented the victims in the WGI case (Warszawska Grupa Inwestycyjna, the Warsaw Investment Group), one of the longest criminal cases in the history of the Polish financial market, because some things must not be left half finished, even when they take two decades. In the case of the collapsed cryptocurrency exchange Zonda (Zondacrypto, operated by BB Trade Estonia OÜ), he represents several hundred victims in the criminal investigation conducted by Poland’s National Prosecutor’s Office and in the Estonian bankruptcy proceedings.

Kancelaria Prawna Skarbiec is listed in the rankings of Poland’s largest tax advisory firms published by Dziennik Gazeta Prawna and Rzeczpospolita, and it is a four-time recipient (2015 to 2018) of the European Medal awarded by the Business Centre Club and the European Economic and Social Committee. Robert Nogacki publishes regularly, in the press and on the firm’s website, for people who have a problem rather than a law degree, because a legal opinion the client cannot understand protects only the lawyer.

He believes that the best legal advice is the kind that means the client never has to appear in court.