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

The principles governing the gathering of evidentiary material constitute the foundation of fair and lawful tax proceedings under Polish law. Pursuant to Article 187 § 1 of the Tax Ordinance (Ordynacja podatkowa), the tax authority is obligated to gather and exhaustively consider the entirety of the evidentiary material. This ostensibly straightforward norm encompasses an elaborate legal architecture, the violation of which represents one of the most frequent grounds for annulment of tax decisions by appellate authorities and administrative courts.

I. The Principle of Objective Truth as the Foundation of Evidentiary Proceedings

The obligation to exhaustively gather evidentiary material constitutes a particularization of the principle of objective (material) truth, articulated in Article 122 of the Tax Ordinance. This principle mandates that tax authorities undertake all necessary actions to achieve precise clarification of the factual circumstances of the matter.

As the Voivodeship Administrative Court in Gliwice observed in its judgment of September 24, 2025 (Case No. I SA/Gl 118/25):

“The establishment and assessment of evidentiary material with respect to all aspects of a tax matter significant for resolution constitutes the competence of authorities conducting tax proceedings. It falls to them to gather evidentiary material to a degree sufficient for the needs of resolution.”

The tax authority may not conduct proceedings in a unilateral manner—oriented toward a predetermined fiscal objective. It is impermissible to gather exclusively those items of evidence that confirm the thesis of tax liability while simultaneously disregarding evidence favorable to the taxpayer. Such conduct would contravene the fundamental requirements of procedural fairness that undergird the administrative process.

II. The Scope of the Duty to Gather Evidence

A. Boundaries of the Authority’s Evidentiary Activity

The obligation to gather evidentiary material does not possess unlimited character. As the Supreme Administrative Court emphasized in its judgment of March 5, 2025 (Case No. II FSK 38/25):

“The tax authority’s obligation to undertake all necessary actions for precise clarification of the factual circumstances of the matter, including the obligation to gather and consider evidentiary material exhaustively, does not, however, possess unlimited or absolute character.”

The Voivodeship Administrative Court in Wrocław, in its judgment of March 7, 2025 (Case No. I SA/Wr 392/25), further refined this principle:

“The principle of objective truth, together with the principles of evidentiary completeness and confidence in the authority, does not impose upon authorities an unlimited obligation to conduct evidentiary proceedings—particularly proceedings directed toward proving theses favorable to the taxpayer. Tax authorities should undertake all actions directed toward clarification of the factual circumstances, but these must be only necessary actions.”

The boundary of evidentiary proceedings is therefore the gathering of evidence that is adequate and sufficient for making factual findings consistent with truth. Tax authorities gather and supplement evidentiary material only until the moment of obtaining certainty regarding the factual circumstances of the matter—a standard that balances thoroughness against administrative efficiency.

B. The Principle of Evidentiary Completeness

The principle of evidentiary completeness (zasada zupełności materiału dowodowego) does not signify an obligation to conduct evidentiary proceedings ad infinitum. As the Voivodeship Administrative Court in Kraków explained in its judgment of July 29, 2025 (Case No. I SA/Kr 342/25):

“The principle of evidentiary completeness does not mean that evidentiary proceedings should be conducted even where the totality of circumstances revealed in the matter suffices for reaching a resolution. The mere submission of evidentiary motions by the party does not automatically necessitate their acceptance and execution.”

Evidentiary material is complete when it contains all evidence necessary for constructing a correct factual basis for resolution of the matter. The tax authority bears no obligation to conduct evidence where circumstances significant for the matter have already been sufficiently established through other evidence.

III. The Burden of Proof in Tax Proceedings

A. The Inquisitorial Principle

Polish tax proceedings operate upon an inquisitorial model rather than an adversarial one. This signifies that the principal burden of gathering evidentiary material rests upon the tax authority. The authority may not transfer this obligation to the taxpayer nor confine itself to evidence presented exclusively by one party.

As the Voivodeship Administrative Court in Poznań indicated in its judgment of February 27, 2025 (Case No. I SA/Po 423/24):

“It is the authorities that are obligated to undertake all necessary actions for precise clarification of the factual circumstances and disposition of the matter.”

This inquisitorial character reflects the understanding that tax proceedings implicate public interests that transcend the immediate controversy between authority and taxpayer, necessitating independent investigation rather than mere adjudication of competing claims.

B. The Taxpayer’s Duty of Cooperation

The inquisitorial character of proceedings does not, however, relieve the taxpayer of the duty to cooperate with the authority. The Voivodeship Administrative Court in Kraków, in its judgment of March 31, 2025 (Case No. I SA/Kr 145/25), emphasized:

“In tax proceedings, emphasis is placed upon the principle of cooperation. If a taxpayer contests a factual circumstance accepted by the authority, it is upon that taxpayer that the obligation rests to justify their position, inter alia, through presentation of appropriate evidence.”

The Voivodeship Administrative Court in Bydgoszcz, in its judgment of March 4, 2025 (Case No. I SA/Bd 865/24), developed this reasoning:

“The tax authority bears no unlimited obligation to seek evidence favorable to the taxpayer—particularly where the taxpayer has undertaken no efforts to protect their interests and has not submitted appropriate evidence to the authority. In consequence, a party that has not adduced sufficient evidence bears the risk of an unfavorable resolution.”

The taxpayer should therefore actively participate in evidentiary proceedings, particularly when possessing evidence supporting their position. Passivity in this regard may result in adverse procedural consequences—a principle that balances the inquisitorial model against legitimate expectations of party engagement.

IV. Consideration of Evidentiary Material

A. The Obligation of Comprehensive Evidence Assessment

Gathering evidentiary material constitutes merely the first stage. Equally significant is its exhaustive consideration. The Voivodeship Administrative Court in Gdańsk, in its judgment of March 11, 2025 (Case No. I SA/Gd 921/24), explained:

“A situation of failure to consider the entirety of evidentiary material obtains where the authority altogether refrains from conducting assessment of evidence—not where it deems particular evidence unreliable and the conclusions flowing from conducted evidence as not constituting the basis for factual findings.”

The tax authority must therefore address each item of gathered evidence. It may deem evidence unreliable, but must provide justification therefor. Omission of evidence without any assessment constitutes violation of Article 187 § 1 of the Tax Ordinance and provides grounds for annulment upon review.

B. Free Assessment of Evidence

Pursuant to Article 191 of the Tax Ordinance, the tax authority assesses, on the basis of the entirety of gathered evidentiary material, whether a given circumstance has been proven. The Supreme Administrative Court, in its judgment of March 5, 2025 (Case No. II FSK 38/25), described in detail the boundaries of this discretion:

“Pursuant to the principle of free assessment of evidence, tax authorities are not constrained by rules concerning the value of particular items of evidence. Authorities adjudicate on the basis of their own conviction, supported by principles of knowledge and life experience. In order that the boundaries of arbitrariness not be exceeded within the scope of this freedom, the tax authority should be guided by principles of logic, conformity of assessment with laws of science and life experience, treatment of gathered evidence as objective phenomena, and comprehensiveness of assessment.”

This formulation echoes principles familiar from comparative evidence law while adapting them to the specific context of administrative tax proceedings.

V. The Principle In Dubio Pro Tributario

Doubts regarding factual circumstances that cannot be eliminated should be resolved in favor of the taxpayer—in accordance with the principle in dubio pro tributario. This principle, articulated in Article 2a of the Tax Ordinance and Articles 10-11 of the Entrepreneurs’ Law Act, constitutes a significant procedural safeguard for the taxpayer.

Inadequate clarification of factual circumstances may not serve as the basis for findings adverse to the party. The tax authority should ground its assertions upon persuasive evidentiary material. As the Supreme Administrative Court in Wrocław indicated in its judgment of July 27, 1994 (Case No. SA/Wr 648/94):

“In its factual findings, the tax authority may not rely upon presumptions. Presumption of a factual circumstance denied by the taxpayer constitutes violation of procedural provisions.”

This principle operates as a tie-breaker of sorts: where genuine uncertainty persists after exhaustive investigation, the taxpayer receives the benefit of that uncertainty rather than bearing its burden.

VI. Consequences of Violating Evidence-Gathering Principles

A. Defectiveness of Decisions

Violation of the obligation to exhaustively gather and consider evidentiary material results in defectiveness of the tax decision. As established jurisprudence of administrative courts confirms:

“Failure by a state administrative authority to undertake procedural actions directed toward gathering complete evidentiary material—particularly where the party invokes specific circumstances significant for it—constitutes a procedural deficiency resulting in defectiveness of the decision” (Supreme Administrative Court judgment of March 19, 1981, Case No. SA 234/81).

“Neglect by a state administrative authority consisting in failure to fulfill the obligation to gather complete evidentiary material constitutes a procedural defect justifying annulment of the decision issued as a result of such neglect” (Supreme Administrative Court judgment of June 11, 1981, Case No. SA 503/81).

B. The Scale of the Problem

Data from the Supreme Audit Office (Najwyższa Izba Kontroli) indicate the systemic character of violations of evidentiary procedure principles by tax authorities. In its 2019 report concerning legal barriers to development of family businesses, the NIK indicated that among the principal causes for annulment of tax decisions are:

• deficiencies in evidentiary material,
• failure to clarify all circumstances of the factual situation,
• erroneous determination of tax liability amounts,
• insufficient proof that the entrepreneur did not act in good faith.

The NIK found violations of principles governing conduct of tax proceedings in half of the audited tax offices. In total, fully 45% of first-instance tax authority decisions were annulled by appellate authorities or administrative courts—a striking figure that underscores the practical significance of evidentiary standards.

VII. Special Evidentiary Issues

A. Expert Evidence

Where a matter requires specialized knowledge, the tax authority may appoint an expert. The Supreme Administrative Court, in its judgment of February 19, 2025 (Case No. III FSK 1007/23), explained:

“The word ‘may’ employed in Article 197 § 1 of the Tax Ordinance signifies that discretion is left to the authority in utilizing expert opinions. The boundaries of exercising this discretion are delineated by the principle of objective truth. The tax authority is obligated to utilize this evidentiary means in matters involving complex factual circumstances that can be clarified only when specialized knowledge is available.”

Simultaneously, the Supreme Administrative Court emphasized that the expert is not appointed to establish factual circumstances or to provide their legal assessment—these functions belong exclusively to the tax authority. The expert’s role is confined to providing specialized technical or scientific input upon which the authority’s own factual and legal determinations may be grounded.

B. Facts Not Requiring Proof

Article 187 § 3 of the Tax Ordinance provides exceptions to the principle that assertions of fact must flow from conducted evidence. Proof is not required for:

• facts of common knowledge (facta notoria)—known to the authority, the party, and the general public alike;
• facts known to the authority ex officio—of which the authority gained knowledge in connection with performance of its duties.

In the case of facts known ex officio, the authority bears an obligation to communicate them to the party in order to afford opportunity for response—a requirement grounded in fundamental principles of procedural fairness.

VIII. Practical Guidance for Taxpayers

A. During Tax Audits and Proceedings

A taxpayer participating in a tax audit or customs and fiscal audit should:

1. Actively participate in evidentiary proceedings—submit motions for conduct of evidence significant for the matter, particularly evidence supporting the taxpayer’s position.
2. Document argumentation thoroughly—all assertions should find support in evidence; mere denial of authority findings without presentation of counter-evidence may prove ineffective.
3. Monitor completeness of evidentiary material—verify whether the authority has gathered all significant evidence, including evidence favorable to the taxpayer.
4. Exercise the right to be heard—before issuance of a decision, the taxpayer possesses the right to comment upon gathered evidentiary material; this represents the final opportunity to identify evidentiary deficiencies.

B. In Appellate Proceedings

In an appeal against a tax decision, the taxpayer should precisely indicate:

• which items of evidence were omitted by the first-instance authority,
• which circumstances significant for the matter were not clarified,
• which factual findings are inconsistent with gathered evidentiary material,
• how these violations may have influenced the outcome of the matter.

C. In Administrative Court Proceedings

In a complaint to the Voivodeship Administrative Court, allegations concerning violation of Article 187 § 1 of the Tax Ordinance should be formulated with precision. As the Supreme Administrative Court indicated in its judgment of March 11, 2025 (Case No. II FSK 886/22):

“If the court of first instance concluded that tax authorities conducted evidentiary proceedings in an improper manner, it should indicate specific, detailed provisions of the Tax Ordinance regulating establishment of factual circumstances in the course of evidentiary proceedings.”

IX. Conclusion: The Centrality of Evidentiary Standards

The principles governing evidence gathering in Polish tax proceedings reflect a sophisticated balance between competing values: the state’s legitimate interest in accurate determination of tax liabilities, the taxpayer’s right to fair process, and the administrative imperative of efficient case resolution. The inquisitorial model places primary responsibility upon the authority while preserving meaningful obligations of cooperation for the taxpayer.

The jurisprudential developments of 2025 demonstrate continued refinement of these principles, with courts articulating increasingly nuanced standards for both the scope of investigative duties and the boundaries beyond which those duties do not extend. The consistent theme across this body of law is that evidentiary proceedings must be thorough but not interminable, comprehensive but not redundant.

For practitioners, mastery of these evidentiary standards is essential. The high rate of decision annulments attributable to evidentiary deficiencies—nearly half of all contested decisions, according to NIK data—underscores that this is not merely an academic concern but a practical reality of tax litigation in Poland.

X. Professional Assistance

The Skarbiec Law Firm provides comprehensive assistance regarding:

• representation during tax audits and customs and fiscal audits,
• participation in tax proceedings as party representative,
• preparation of evidentiary motions and procedural submissions,
• drafting of appeals against tax decisions,
• representation before administrative courts and the Supreme Administrative Court.

In matters concerning tax disputes, early engagement of professional counsel is particularly significant—counsel who will ensure proper documentation of the taxpayer’s position from the audit stage forward, when the evidentiary foundation for subsequent proceedings is established.

Robert Nogacki

Founder and Managing Partner of Skarbiec Law Firm, recognized by Dziennik Gazeta Prawna as one of the best tax advisory firms in Poland (2023, 2024). Legal advisor with 19 years of experience, serving Forbes-listed entrepreneurs and innovative start-ups. One of the most frequently quoted experts on commercial and tax law in the Polish media, regularly publishing in Rzeczpospolita, Gazeta Wyborcza, and Dziennik Gazeta Prawna. Author of the publication “AI Decoding Satoshi Nakamoto. Artificial Intelligence on the Trail of Bitcoin’s Creator” and co-author of the award-winning book “Bezpieczeństwo współczesnej firmy” (Security of a Modern Company). LinkedIn profile: 18 500 followers, 4 million views per year. Awards: 4-time winner of the European Medal, Golden Statuette of the Polish Business Leader, title of “International Tax Planning Law Firm of the Year in Poland.” He specializes in strategic legal consulting, tax planning, and crisis management for business.