September 11, 2025, will be a special day for Polish borrowers. The Advocate General of the Court of Justice of the European Union presented his opinion in Case C-471/24 (JJ v. PKO BP SA), which concerns a WIBOR-based mortgage loan.
WIBOR – an invisible mechanism in every installment
, WIBOR, or the Warsaw Interbank Offered Rate , determined the interest rate on zloty loans. It was intended to reflect the real cost of loans between banks. In practice, however, it was largely based on declarations, often unsupported by actual transactions. For consumers, this meant that the installment amount depended on an index they neither understood nor could verify.
Preliminary questions from a Polish court
The District Court in Częstochowa submitted four questions of fundamental importance to the Tribunal:
- Can the provisions of a loan agreement based on WIBOR be controlled for unfairness?
- Are such provisions – even if they refer to the main terms of the contract – subject to court review?
- Does the lack of reliable information to the consumer about the risk of a variable interest rate and the non-transparent method of determining the index violate the contractual balance of the parties?
- If these clauses are deemed abusive, can the agreement continue to apply only with the bank's margin, which would in practice lead to the loan being transformed into a fixed-rate product?
These are questions that concern not only one individual case, but the structure of thousands of contracts concluded by Polish families.
Opinion of the CJEU Advocate
The Advocate General confirmed that:
- WIBOR-based clauses can be examined by courts – they are not exempt from scrutiny;
- banks are obliged to reliably inform consumers about the risk of a variable rate, the principles of operation of the index and its financial consequences;
- lack of transparency means the risk of the provisions being considered unfair and disturbing the balance of the parties.
At the same time, it was noted that the assessment did not concern the WIBOR index itself, but the way in which banks introduced it into contracts and informed customers about it.
The role of the Ombudsman's opinion
Although the opinion is not binding, experience in judicial practice shows that in the vast majority of cases, the CJEU follows this direction. Therefore, we can already speak of a breakthrough – this opinion sends a clear signal to national courts and provides real hope for PLN borrowers.
Two periods of disputes over WIBOR
When analyzing the WIBOR issue, two stages must be distinguished. The first is before GPW Benchmark (formerly ACI Polska) took over the administrator's role, when allegations of a lack of transactionality were particularly strong. The second is after the entry into force of the BMR regulation, which introduced EU standards for benchmarks. An assessment of both of these periods will determine the situation of thousands of consumers who concluded agreements in different years.
Echo of the Swiss franc issues
The history of Swiss franc loans demonstrates that only the intervention of the European Court of Justice (CJEU) paved the way for broad consumer protection in Poland. Today's opinion raises the question of whether a similar scenario will repeat itself with WIBOR-based loans. If the line indicated by the Ombudsman is confirmed in the judgment, the consequences could be comparable – for both borrowers and the banking sector.
Summary
The opinion of the Advocate General of the European Court of Justice (CJEU) does not yet resolve the matter, but it is already a turning point. For the first time, it has been clearly confirmed that the WIBOR mechanism is not beyond the reach of judicial review and that consumers must be properly informed of the risks. This opens a new chapter in credit disputes, which in the long term could lead to real changes in the situation of borrowers and a fundamental overhaul of banking practice in Poland.
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