WIBOR in Polish courts: more challenges to the benchmark itself rejected after EU court ruling

Since the Court of Justice of the EU ruling of 12 February 2026 (case C-471/24), Polish courts have increasingly rejected objections to the WIBOR benchmark itself. They focus instead on whether a particular loan contract is clear to the customer. This is according to an analysis by Marcin Bartczak and Marek Trzos-Rastawiecki, partners at the law firm ITMA, published on 20 October 2026 in "Rzeczpospolita".

What the CJEU decided

According to the authors, the Court separated three issues that were often treated together:

• a variable interest clause tied to a regulated benchmark can be reviewed by courts under Directive 93/13/EEC, but the possibility of review does not mean the clause is unfair;
• a bank does not have to explain to the consumer how WIBOR is calculated. It is responsible for information about the contract: how interest is set, how it may change and what this means for the borrower. The benchmark's administrator is responsible for information about the methodology;
• a bank's participation in supplying data to the benchmark, and the use of data that does not come solely from real transactions, does not make a clause unfair if the benchmark complied with the EU BMR regulation when the contract was signed.

The authors stress that this is not unconditional approval of every contract, nor a ruling on all periods in which the benchmark operated.

What the September rulings show

The authors reviewed rulings published in September 2026. Their monitoring found five concerning WIBOR. Four contain assessments favourable to the banks' arguments. The fifth concerns a flawed leasing contract. They caution that this refers to publication dates rather than the dates of judgments, and that it is not full statistics for cases across the country.

The Regional Court in Łódź (II C 528/26) held that the bank could not shape the benchmark within the contract. The Regional Court in Warsaw (I C 350/19) found that combining WIBOR with a fixed margin does not give the bank the right to set interest arbitrarily. The bank nevertheless lost that case on other grounds.

The District Court in Toruń (I C 1360/25) noted that the contract stated the margin, the benchmark, the reading date and the rules for changing interest, so there was no need to attach the benchmark's full rulebook. The Court of Appeal in Lublin, in a judgment of 14 September 2026 (I ACa 989/25), found no legal basis for requiring a bank to explain in detail how the WIBOR rate is determined. In that case it also mattered that the objections about information were raised only on appeal.

A flawed contract is a separate matter

A ruling of the District Court in Konin (V GC 659/22), published on 15 September, went against the bank. It concerned a leasing contract that did not sufficiently set out how interest is determined and updated, how instalments are calculated, or the information needed to verify the amounts due. According to the authors, the problem was the construction of that contract, not WIBOR itself. Defective provisions are not cured by referring to a regulated benchmark.

The authors say five publications do not allow anyone to declare the disputes over. But in their view a settling way of thinking among courts is visible: the specific contract, the information duties and the legal situation at the time of signing are examined, and a general objection that WIBOR is flawed is not enough.

What this means for readers with loans in Poland

This concerns people who have a zloty loan in Poland based on WIBOR and are considering a dispute with their bank. The analysis suggests the outcome more often depends on the wording of their contract and the information they received from the bank than on the benchmark's design. This is not legal advice, and each contract is assessed individually.