WIBOR litigation, part 1: Can the WIBOR benchmark be challenged as the basis for setting variable interest rates?
Variable interest rate loans based on the WIBOR benchmark are a major part of the Polish financial market. For years the WIBOR rate remained at a low level, but it shot up in 2022. The WIBOR 6M stood at 0.25% in January 2021, but by July 2022 it had hit a peak of 7.43%. Currently the WIBOR 6M is a little lower (5.05% as of 10 June 2025), but it has yet to retreat to its earlier low values.
This sudden jump translated into much higher loan repayment instalments, which sparked a broad debate on the legality of using WIBOR as an element for setting the interest rate on loans to consumers, as well as banks’ compliance with their informational obligations.
Litigation to date in Poland
Some consumer borrowers resort to the courts in an effort to undermine the provisions of credit agreements using variable interest rates based on WIBOR, hoping that the courts will recognise these interest provisions as impermissible contractual clauses under Civil Code Art. 3851. If successful, such challenges could result in a finding that credit agreements as a whole, or specific WIBOR provisions, are ineffective, leading to an advantageous economic result for borrowers similar to that achieved in earlier litigation over credit denominated in Swiss francs, issued by Polish banks to consumers.
According to media reports, as of the end of March 2025 there were 1,755 cases pending in Polish courts concerning WIBOR-based mortgage loans. This is not very many compared to the overall number of variable-interest loan agreements based on WIBOR. One reason may be that dozens of rulings have already been issued in WIBOR cases, with the great majority coming down against the borrowers (see T. Nowakowski, “Overview of current rulings in WIBOR cases,” LEX/el. 2025). But some of those proceedings have been stayed while the national courts wait for the Court of Justice of the European Union to take a position on this issue, as the Częstochowa Regional Court (in case no. I C 1226/23) decided to submit a request for a preliminary ruling to the Court of Justice concerning allegedly abusive contractual clauses using WIBOR as the basis for setting variable interest rates.
The Court of Justice will consider the issue of WIBOR loans in light of Council Directive 93/13/EEC of 5 April 1993 on unfair terms in consumer contracts (Case C-471/24, PKO BP). Because Directive 93/13/EEC was implemented into Polish law via Civil Code Art. 385¹, among other provisions, and the Polish courts have an obligation to interpret national regulations consistently with EU law, how this directive is interpreted by the Court of Justice will—as in the case of CHF-denominated loans—be of key importance for Polish courts deciding WIBOR cases.
The allegations raised by borrowers against credit agreements with variable interest rates based on WIBOR can be divided into two main categories. The first concerns the WIBOR benchmark itself, the legality of using it in credit agreements with consumers, and the supposed irregularities in how WIBOR is set. The second group focuses on the alleged abusiveness (under Civil Code Art. 385¹) of contractual clauses basing variable interest rates on WIBOR, including the banks’ alleged failure to comply with their duty to provide information to customers.
We will discuss the Civil Code provisions on abusive clauses in a separate article.
What is WIBOR?
Given the objections being asserted to the legality of using the WIBOR benchmark, as well as the legality of how it is determined, it is worth exploring some basic issues related to this benchmark.
WIBOR (the Warsaw Interbank Offered Rate) is a benchmark derived from the Polish interbank market. It indicates the interest rate at which banks could deposit funds with other banks for a definite period. It is commonly used to set variable interest rates on loans—both consumer credit and mortgage credit. WIBOR is also used in other financial instruments, such as treasury bonds and corporate bonds, instalments in finance leases, and investment instruments, and consequently it is crucial for the whole Polish financial system.
WIBOR has functioned since the 1990s. Since 30 June 2017 WIBOR has been administered by GPW Benchmark S.A., a subsidiary of the company operating the Warsaw Stock Exchange. Before that it was administered by ACI Polska.
Since 16 December 2020 WIBOR has also been a “critical benchmark” for purposes of the Benchmark Regulation or BMR (Regulation (EU) 2016/1011 of the European Parliament and of the Council of 8 June 2016 on indices used as benchmarks in financial instruments and financial contracts or to measure the performance of investment funds). The BMR was intended to ensure the accuracy and integrity of indices and benchmarks used in the European Union, while achieving a high level of protection of consumers and investors and efficient functioning of the internal market, in particular financial markets (see J. Sewerynik, “WIBOR: The legal characteristics of the benchmark in the context of the Benchmark Regulation and selected objections to the legality of applying it,” Przegląd Prawa Handlowego no. 4/2024, p. 32).
Recognition of WIBOR as a critical benchmark under the BMR carries a series of legal and regulatory consequences. The BMR also sets forth the requirements for the input data from which the given benchmark is calculated.
How is WIBOR set?
WIBOR is determining using a methodology strictly defined in GPW Benchmark’s “Regulations for the WIBID and WIBOR Reference Rates.” The process for determining the WIBOR for a given day is referred to as the “fixing.” On each business day, the biggest banks operating in Poland, which are participants in the WIBOR panel, submit declarations of the interest rate at which they would be willing to lend money to other banks for specified periods. This data is used to set the WIBOR for various terms: overnight (O/N), tomorrow/next (T/N), one week (1W), one month (1M), three months (3M), six months (6M), and one year (1Y).
As a rule, the data for calculating WIBOR should involve real transactions, but if such data is not available or adequate, verifiable non-transactional data may be used instead (Sewerynik, p. 33). From the quotes submitted by the banks on the panel, the extreme values (highest and lowest) are excluded, and the arithmetic mean of the remaining values is determined. This result constitutes the WIBOR for the given period. On each fixing date, the indicator is published on the GPW Benchmark S.A. website. However, if fewer than six banks participating in the fixing submit quotes, no indicator is set.
This procedure has been used to set the WIBOR since its reform in connection with implementation of the BMR, i.e. since 16 December 2020. But this does not mean that the WIBOR from before that date was defective (in this article we do not discuss the earlier method of calculating WIBOR).
Significantly, the characteristics of the WIBOR benchmark described above are also noted by the Polish courts rejecting consumers’ challenges to the legality of WIBOR and the correctness of the method used to calculate it.
Objections to WIBOR
One of the allegations raised against WIBOR is that it is based not on actual transactions on the interbank market, but on arbitrary quotes from banks who have a conflict of interest (Sewerynik, p. 34). This questions WIBOR’s compliance with the EU’s Benchmark Regulation. But there are serious doubts whether the civil courts have any authority to examine the correctness of the method for calculating the benchmark, because the courts are bound by a legally final administrative decision.
As the Gliwice Regional Court found in July 2024 (case no. I C 308/24), the jurisprudence from the Supreme Court of Poland is unequivocal in this respect: a final administrative decision is binding on the civil courts, and if it is stated in a final decision by the Polish Financial Authority (KNF) that the methodology for determining WIBOR meets the requirements of the BMR, the court cannot re-examine the issue of the type of data a given benchmark was based on (see KNF decision of 16 December 2020 and the related KNF communiqué of 17 December 2020). Thus it is sometimes argued that the legality of WIBOR is not subject to review by the civil courts in disputes between consumers and their lenders.
Generally the Polish courts also reject the claim that banks are in a position to unilaterally set the WIBOR indices (echoing claims in the litigation by CHF borrowers that banks had latitude when setting the forex rates which carried over to the amount of instalments that mortgage borrowers had to pay). The courts point out that the process of determining the WIBOR (fixing) has multiple stages and is based on data submitted by numerous banks belonging to the panel, greatly restricting the influence of any one participant (see Sewerynik, p. 36). And banks that are not on the panel have no influence over the level of the benchmark.
For example, as the Olsztyn Regional Court held: “The market reference rate WIBOR 3M is not subject to negotiation by the parties, nor is it set arbitrarily by the plaintiff bank, but it arises on the basis of the interbank market and is dependent on factors such as inflation and the interest rates set by the Monetary Policy Council” (case no. I C 162/22, and similarly in cases I C 523/23 and I C 425/23).
The Poznań Court of Appeal stressed (case no. I ACa 368/22) that the WIBOR is a value over which neither of the parties to a credit agreement have any direct influence. Thus the court recognised that the mechanism for establishing WIBOR is too complicated and regulated to allow any arbitrary influence by a single bank on the WIBOR, the value of which is determined on the basis of objective, external market factors.
Request to the Court of Justice for a preliminary ruling (C-471/24, PKO BP)
As mentioned in the introduction, many courts in Poland are anticipating an interpretation of Directive 93/13/EEC by the Court of Justice (which is solely empowered to interpret EU law). The ruling should resolve doubts about the alleged abusiveness of contractual provisions adopting WIBOR as the basis for determining variable interest rates.
In this respect, the Częstochowa Regional Court filed a request for a preliminary ruling with the Court of Justice on 3 July 2024. The Polish court posed four questions:
- Must Art. 1(2) of Council Directive 93/13/EEC be interpreted as permitting examination of contractual clauses concerning a variable interest rate based on the WIBOR reference index?
- If the answer to the first question is in the affirmative, must Art. 4(2) of Council Directive 93/13/EEC of 5 April 1993 on unfair terms in consumer contracts be interpreted as permitting examination of contractual clauses concerning a variable interest rate based on the WIBOR reference index?
- If the answers to the first and second questions are in the affirmative, must Art. 3(1) of Council Directive 93/13/EEC be interpreted as meaning that a contractual clause concerning a variable interest rate based on the WIBOR reference index may be regarded as contrary to the requirement of good faith and causing a significant imbalance in the parties’ rights and obligations under the contract, to the detriment of the consumer, on account of the failure duly to inform the consumer of his or her exposure to the risk of a variable interest rate, in particular the failure to indicate how the reference index, which forms the basis for determining the variable interest rate, is determined and what uncertainties are associated with its non-transparency and the uneven distribution of that risk between the parties to the contract?
- If the answers to the previous questions are in the affirmative, must Art. 6(1) of Council Directive 93/13/EEC, in conjunction with Art. 3 (1) and (2), second sentence, and Art. 2 thereof, be interpreted as meaning that, if a contractual clause concerning a variable interest rate based on the WIBOR reference index is found to be unfair, there can be continued operation of a contract in which the interest rate on the amount of the loan capital will be based on a second component determining the interest rate included in the contract, that is to say the bank’s fixed margin, which will change the interest rate on the loan from variable to fixed?
The answers from the Court of Justice will be crucial for the Polish courts seeking to resolve WIBOR cases. Although Directive 93/13/EEC is not directly applied in the Polish legal system, it was transposed into Polish law by (among other provisions) Civil Code Art. 4851, concerning prohibited contractual clauses. Under the well-established precedent of the Court of Justice, national courts applying internal law, particularly provisions transposing a directive into national law, should as far as possible interpret national law in a manner consistent with EU law (e.g. C-14/83, von Colson). This means that Polish courts applying Civil Code Art. 4851 in the WIBOR cases are obliged to interpret this provision consistent with the wording and purpose of Directive 93/13/EEC.
The hearing in the case before the Court of Justice initiated by the request from the Częstochowa Regional Court was held on 11 June 2025. It was the first hearing before the Court of Justice in a WIBOR case. After considering the positions of the parties, as well as representatives of the European Commission, the Polish government, and the Portuguese government, the court decided to seek an opinion from the advocate general, which is to be presented on 11 September 2025. A judgment in C-471/24, PKO BP, should thus be expected no earlier than mid-2026.
Summary
In light of the nature of the WIBOR benchmark and the EU’s Benchmark Regulation, consumers’ challenges to the legality and the correctness of calculation of WIBOR should not be upheld.
The national courts sometimes point out, correctly, that they cannot even examine whether the method of calculating the benchmark is lawful, because the regulatory body (KNF) has issued a legally final administrative decision recognising the process of setting the WIBOR benchmark as consistent with the requirements imposed by EU law (e.g. Gliwice Regional Court judgment of 8 July 2024, case no. I C 308/24).
In turn, the allegation that certain banks could arbitrarily influence the level of the WIBOR is inconsistent with the nature of this benchmark, particularly the “fixing” process for calculating it (see Sewerynik, p. 36). Here we should also mention the assessment of the WIBOR critical benchmark carried out by KNF for the period of 1 December 2022 – 31 December 2024, which found that “WIBOR maintains the capacity to measure the market, and the economic realities which it was established to measure.”
The argument that applying WIBOR to the interest rates on consumer credit results in an unequal allocation of risk is also unfounded. As the Polish courts have correctly pointed out, “the risk of a change in the WIBOR benchmark is borne equally by both parties to the contract, and not just the borrower” (Gdynia District Court judgment of 30 September 2024, case no. I C 654/23).
On the issue of the possibility of applying Art. 3851 §1 of the Polish Civil Code to contractual provisions adopting WIBOR as the basis for determining variable interest rates, the final word lies with the Court of Justice and its answer to the request for a preliminary ruling submitted by the Polish court.
Mateusz Kosiorowski, adwokat, Anna Szczęsna, Dispute Resolution & Arbitration practice, Wardyński & Partners
