Provisional text

JUDGMENT OF THE COURT OF JUSTICE (Ninth Chamber)

10 September 2026 (*)

( Reference for a preliminary ruling – Consumer protection – Directive 93/13/EEC – Unfair terms in consumer contracts – Article 6(1) and Article 7(1) – Mortgage loan agreement denominated in a foreign currency and containing unfair terms – Effects of a term being found to be unfair – Contract declared void – Action brought by the consumer for repayment of the amounts paid under the contract – Claim of the seller or supplier corresponding to the amount of capital lent – National case-law providing for the set-off ex officio of reciprocal claims of the parties to a void agreement – National case-law providing for the creation of two independent claims for restitution – Deterrent effect of the prohibition on unfair terms )

In Case C‑510/25 [Adazik], (i)

REQUEST for a preliminary ruling under Article 267 TFEU from the Sąd Okręgowy w Warszawie (Regional Court, Warsaw, Poland), made by decision of 28 July 2025, received at the Court on the same day, in the proceedings

T.Z.,

D.Z.

v

Bank S.A.,

THE COURT (Ninth Chamber),

composed of M. Condinanzi, President of the Chamber, R. Frendo (Rapporteur) and A. Kornezov, Judges,

Advocate General: R. Norkus,

Registrar: A. Calot Escobar,

having regard to the written procedure,

after considering the observations submitted on behalf of:

–        T.Z. and D.Z., by R. Górski, radca prawny,

–        Bank S.A., by P. Haiduk, B. Miąskiewicz and M. Romanowski, adwokaci, and by A. Cudna-Wagner, radca prawny,

–        the Polish Government, by B. Majczyna, acting as Agent,

–        the European Commission, by M. Brauhoff and P. Kienapfel, acting as Agents,

having decided, after hearing the Advocate General, to proceed to judgment without an Opinion,

gives the following

Judgment

1        This request for a preliminary ruling concerns the interpretation of Article 6(1) and Article 7(1) of Council Directive 93/13/EEC of 5 April 1993 on unfair terms in consumer contracts (OJ 1993 L 95, p. 29).

2        The request has been made in proceedings between T.Z. and D.Z., two consumers (‘the borrowers’), and Bank S.A., a bank, concerning the repayment of amounts paid to Bank S.A. under a mortgage loan agreement rendered invalid by the presence of unfair terms.

 Legal context

 European Union law

3        Under the twenty-fourth recital of Directive 93/13:

‘… the courts or administrative authorities of the Member States must have at their disposal adequate and effective means of preventing the continued application of unfair terms in consumer contracts’.

4        Article 6(1) of Directive 93/13 provides:

‘Member States shall lay down that unfair terms used in a contract concluded with a consumer by a seller or supplier shall, as provided for under their national law, not be binding on the consumer and that the contract shall continue to bind the parties upon those terms if it is capable of continuing in existence without the unfair terms.’

5        Under Article 7(1) of that directive:

‘Member States shall ensure that, in the interests of consumers and of competitors, adequate and effective means exist to prevent the continued use of unfair terms in contracts concluded with consumers by sellers or suppliers.’

 Polish law

6        Article 405 of the ustawa – Kodeks cywilny (Law on the Civil Code) of 23 April 1964 (Dz. U. of 1964, No 16, item 93), in the version applicable to the dispute in the main proceedings (‘the Civil Code’), provides:

‘Any person who, without legal grounds, obtains an economic advantage at the expense of another person shall be required to restore that advantage in kind and, where that is not possible, to return the value thereof.’

7        Article 410 of that code provides:

‘§1.      The provisions of the preceding articles shall apply in particular to an undue obligation.

§2.      An obligation shall be undue where the person who performed it was in no way obliged or was not obliged to the person for which it was performed, or where the basis of the obligation ceased to exist or the intended objective of the obligation was not attained, or where the legal transaction requiring performance of the obligation was void and did not become valid after the obligation was performed.’

8        Article 455 of the code reads as follows:

‘If the time limit for performing the obligation is not specified or if it does not result from the nature of the obligation, the obligation shall be performed promptly after the debtor has been called upon to perform it.’

9        Under Article 498(1) and (2) of that code:

‘§1.      If two persons are simultaneously and mutually debtors and creditors with respect to each other, each of them may set off their claim against the claim of the other party, if the object of both claims is money or generic goods of the same quality, and both claims are due and can be enforced before a court or other State body.

§2.      As a result of the set-off, the two claims are offset against each other to the extent of the lower claim.’

10      Under Article 499 of the Civil Code:

‘A set-off shall be effected by a declaration submitted to the other party. The declaration shall have retroactive effect from the moment when the set-off became possible.’

 The dispute in the main proceedings and the questions referred for a preliminary ruling

11      On 30 September 2005, the borrowers concluded a mortgage loan agreement with Bank, denominated in Swiss francs (CHF), under which Bank paid them, on 26 October 2005, an amount of 229 685.50 zlotys (PLN) (approximately EUR 54 275) (‘the agreement at issue’).

12      In respect of the performance of that agreement, the borrowers made transfers to Bank in both zlotys and Swiss francs. The total amount paid to Bank is PLN 296 613.33 (approximately EUR 70 000) and CHF 50 579.63 (approximately EUR 55 800).

13      On 29 November 2021, the borrowers, of the view that that agreement was void on account of the unfair terms contained therein, brought an action before the Sąd Okręgowy w Warszawie (Regional Court, Warsaw, Poland), the referring court, in order for it to summon Bank to a hearing concerning an amicable settlement of the dispute, the borrowers seeking repayment of the amounts paid under that contract. On 22 February 2022, a hearing was held before that court but no amicable settlement could be reached.

14      Following the failure of the attempt to reach an amicable settlement, the borrowers asked the referring court to order Bank to repay to them part of the amounts which they had paid to it, including during the period in which the amount of their cumulative payments had not yet exceeded the amount of capital lent. In that context, they claimed that their claim for restitution of the amounts wrongly received by Bank had become due since 23 February 2022, that is to say, the day after the hearing referred to in paragraph 13 above, which constituted formal notice for the purposes of Article 455 of the Civil Code, on which the claim for payment of interest was based.

15      Bank contended that the borrowers’ claim should be dismissed and that they should be ordered to pay the costs, maintaining, inter alia, that the agreement at issue is legally valid.

16      The referring court states that the question of the settlement of the reciprocal claims of the parties to a mortgage loan agreement declared void has given rise to two lines of case-law in Poland, one based on the ‘two claims theory’ and the other on the ‘balance theory’.

17      That court states that, first, according to the two claims theory, applying the combined provisions of Articles 405 and 410 of the Civil Code, each party to such a contract is entitled to claim repayment of the payments made, which must be regarded as undue. That right exists irrespective of the extent to which a party is at the same time liable for repayment of a payment wrongly received by the other party.

18      On the other hand, according to the balance theory, following a declaration that a contract concluded between a consumer and a seller or supplier is void, the consumer’s financial payments must be classified as undue only once the total amount which they represent is greater than that of the capital lent by the seller or supplier. That theory means that the court is to proceed of its own motion to set off the parties’ reciprocal claims up to the lowest amount, without it being necessary for a party to submit a declaration of set-off. In accordance with that theory, there is therefore a single claim in favour of the party to the contract that had a claim of an amount greater than that of the other party’s claim.

19      The referring court explains that the Sąd Najwyższy (Supreme Court, Poland), from 2019 onwards, had advocated the application of the two claims theory, in particular on account of the lack of legal basis, in Polish law, for the balance theory. However, following the judgment of the Court of Justice of 19 June 2025, Lubreczlik (C‑396/24, EU:C:2025:460), certain decisions of the Sąd Najwyższy (Supreme Court) held that Article 6(1) of Directive 93/13 justifies the application of the balance theory.

20      The referring court states that, in the present case, the application of the balance theory would deprive the borrowers of the right to claim repayment of the sums paid to Bank during the period in which the aggregate of those sums remained lower than the amount of capital lent and of interest on those sums. In addition, that court states that in view of the fact that, as is apparent from paragraph 12 of the present judgment, the borrowers made payments to Bank in two different currencies, they are not in a position to state when the capital lent was repaid in full.

21      On a more general level, the referring court considers that the balance theory is liable to have negative consequences for consumers, to the benefit of banks. Thus, it considers that that theory is contrary to the objectives of Directive 93/13 and, consequently, difficult to reconcile with EU law.

22      However, that court states that some Polish case-law interprets the judgment of 19 June 2025, Lubreczlik (C‑396/24, EU:C:2025:460), as meaning that the Court of Justice held that the reciprocal claims of the parties to a loan agreement that has been declared void must be offset of the court’s own motion, in accordance with the balance theory.

23      The referring court doubts whether such an interpretation is correct. Indeed, in that judgment, the Court did not state expressly that the two claims theory is contrary to Directive 93/13. Moreover, according to the referring court, it is apparent from the judgments of 25 November 2020, Banca B. (C‑269/19, EU:C:2020:954), and of 16 March 2023, M.B. and Others (Effects of the invalidation of a contract) (C‑6/22, EU:C:2023:216), that, in the event that a contract concluded between a consumer and a seller or supplier is declared invalid because one of its terms is unfair, it is for the Member States, by means of their national law, to make provision for the effects of that invalidation, in compliance with the protection granted to the consumer by that directive, in particular by ensuring the restoration of the legal and factual situation in which the consumer would have been if that unfair term had not existed.

24      In those circumstances, the Sąd Okręgowy w Warszawie (Regional Court, Warsaw) decided to stay the proceedings and to refer the following questions to the Court of Justice for a preliminary ruling:

‘(1)      Must Article 6(1) read in conjunction with Article 7(1) of [Directive 93/13] be interpreted as precluding the application of an arrangement relating to the settlement between the parties to an invalid loan agreement such that the consumer’s claim for reimbursement of payments made in performance of such an agreement is ex officio set off by the court against the bank’s claim for reimbursement of the loan capital disbursed, with the result that the consumer’s claim arises only when the sum of his or her payments exceeds the amount of the loan capital disbursed to him or her?

(2)      Must Article 6(1) read in conjunction with Article 7(1) of [Directive 93/13] be interpreted as precluding the limitation of the consumer’s right to default interest on all payments made by him or her to the bank in performance of an invalid loan agreement? Furthermore, do those provisions preclude an interpretation of national law to the effect that a consumer is not entitled to default interest on all payments made to the bank in performance of an invalid loan agreement?’

 The application to open the oral part of the procedure

25      By letter lodged at the Court Registry on 24 April 2026, the borrowers requested that the oral part of the procedure be opened, arguing, inter alia, that it was necessary, first, to respond to the written observations of the European Commission relating to the lack of any significant difference, from an economic point of view, between the application of the balance theory and that of the two claims theory and, second, to explain in greater detail the negative consequences of the first of those theories, as applied by several Polish courts, in particular as regards loans repaid in a foreign currency.

26      In that regard, it should be noted that, notwithstanding the requests for a hearing made by the parties to the main proceedings, the Court decided, pursuant to Article 76(2) of its Rules of Procedure, on a proposal from the Judge-Rapporteur and after hearing the Advocate General, not to hold a hearing, considering, on reading the observations lodged during the written part of the procedure, that it had sufficient information to give a ruling in the present case.

27      In addition, it should be borne in mind that, in accordance with Article 83 of the Rules of Procedure, the Court may at any time, after hearing the Advocate General, order the opening or reopening of the oral part of the procedure, in particular if it considers that it lacks sufficient information, or where a party has, after the close of that part of the procedure, submitted a new fact which is of such a nature as to be a decisive factor for its decision, or where the case must be decided on the basis of an argument which has not been debated between the parties or the interested persons referred to in Article 23 of the Statute of the Court of Justice of the European Union.

28      In the present case, the Court considers, after hearing the Advocate General, that none of the situations referred to in Article 83 has arisen and that no other circumstance justifies opening the oral part of the procedure.

29      Consequently, the borrowers’ request must be rejected.

 Consideration of the questions referred

 Admissibility

30      Bank expresses doubts as to the admissibility of the questions referred, on the ground that an answer to them is not necessary to resolve the dispute in the main proceedings. First, applying the balance theory to the dispute would enable the borrowers to obtain the amounts they claim, including interest. Second, Bank submits that the referring court cannot rule ultra petita.

31      In that regard, it should be borne in mind that, according to settled case-law, questions relating to EU law enjoy a presumption of relevance. The Court may refuse to rule on a question referred for a preliminary ruling by a national court only where it is quite obvious that the interpretation of EU law that is sought bears no relation to the actual facts of the main action or its purpose, where the problem is hypothetical, or where the Court does not have before it the factual or legal material necessary to give a useful answer to the questions submitted to it (see judgments of 7 September 1999, Beck and Bergdorf, C‑355/97, EU:C:1999:391, paragraph 22, and of 11 December 2025, Kuszycka, C‑767/24, EU:C:2025:962, paragraph 34).

32      In addition, it is also settled case-law that the national court alone has jurisdiction to find and assess the facts in the case before it and to interpret and apply national law. The Court must take account, under the division of jurisdiction between the Court and the national courts, of the factual and legislative context, as described in the order for reference, in which the questions put to it are set (judgment of 17 October 2024, NFŠ, C‑28/23, EU:C:2024:893, paragraph 31 and the case-law cited).

33      In the present case, first, it is common ground that the questions referred concern the interpretation of provisions of EU law, with the result that they enjoy a presumption of relevance. Second, it is not apparent from the request for a preliminary ruling that, if the balance theory were applied, the borrowers would be fully successful, as Bank claims.

34      Consequently, the questions referred in the present request for a preliminary ruling are admissible.

 Substance

35      By its questions, which it is appropriate to examine together, the referring court asks, in essence, whether Article 6(1) and Article 7(1) of Directive 93/13 must be interpreted as precluding a judicial interpretation of national law according to which the court seised by the consumer of a claim for repayment of amounts paid under a mortgage loan agreement, rendered invalid by the unfair terms contained therein, proceeds of its own motion to set off the reciprocal claims of the consumer and the seller or supplier who are parties to that agreement, with the result that the consumer is recognised as having a claim solely on the amount of the payments made in respect of the performance of that agreement which exceeds the amount of the capital lent and a right to default interest on that excess amount.

36      Under Article 6(1) of Directive 93/13, Member States are to lay down that unfair terms used in a contract concluded with a consumer by a seller or supplier are, as provided for under their national law, not to be binding on the consumer.

37      In addition, given the nature and significance of the public interest constituted by the protection of consumers, who are in a position of weakness vis-à-vis sellers or suppliers, Directive 93/13, as is apparent from Article 7(1) thereof, read in conjunction with its twenty-fourth recital, obliges the Member States to provide for adequate and effective means ‘to prevent the continued use of unfair terms in contracts concluded with consumers by sellers or suppliers’ (judgment of 22 January 2026, Herchoski, C‑902/24, EU:C:2026:42, paragraph 56 and the case-law cited).

38      The Court has held that the consequences that should follow from the finding that a term in a contract concluded between a seller or supplier and a consumer is unfair must allow two objectives to be achieved. First, the court must ensure that the equality between the parties, which would have been undermined if a term of the contract that was unfair as regards the consumer was applied, is restored. Second, it is necessary to ensure that the seller or supplier is deterred from including such terms in contracts with consumers. Accordingly, the obligation for the national court to exclude an unfair contractual term imposing the payment of amounts that prove not to be due entails, in principle, a corresponding restitutory effect in respect of those same amounts (judgment of 27 November 2025, Gryczara, C‑746/24, EU:C:2025:925, paragraph 45 and the case-law cited).

39      In so far as the absence of such an effect would be liable to undermine the deterrent effect that Article 6(1) of Directive 93/13, read in conjunction with Article 7(1) of that directive, seeks to attach to a finding that the terms in contracts concluded with consumers by a seller or supplier are unfair, a similar restitutory effect must be recognised where the unfairness of terms of a contract concluded between a consumer and a seller or supplier results not only in the invalidity of those terms, but also in the invalidity of that contract in its entirety (judgment of 15 June 2023, Bank M. (Consequences of the annulment of the contract), C‑520/21, EU:C:2023:478, paragraph 66 and the case-law cited).

40      While the Court has already defined, on several occasions, the way in which the national court must ensure that the rights which consumers derive from Directive 93/13 are protected, the fact remains that, in principle, EU law does not harmonise the procedures applicable to examining whether a contractual term is unfair or the consequences to be drawn from a finding that such a term is unfair. Thus, in the absence of specific EU rules governing the matter, the means of the implementation of the consumer protection provided for by that directive are governed by the internal legal order of the Member States by virtue of the principle of procedural autonomy of those States. Nevertheless, those means of implementation must not be less favourable than those governing similar domestic actions (principle of equivalence) and may not be framed in such a way as to make it in practice impossible or excessively difficult to exercise the rights conferred by the EU legal order (principle of effectiveness) (judgment of 11 December 2025, Kuszycka, C‑767/24, EU:C:2025:962, paragraph 44 and the case-law cited).

41      It follows from the case-law referred to in paragraphs 38 to 40 above that, subject to ensuring compliance with the restitutory and dissuasive effects required by the application of Directive 93/13 and with the principles of equivalence and effectiveness, a Member State is, in principle, free to choose the way in which it wishes to ensure the consumer protection required by that directive.

42      Consequently, that directive cannot be interpreted as requiring Polish courts to give priority to the application of the balance theory or the two claims theory, the choice in that regard being a matter for those courts, provided that they afford the consumer, in all cases, the protection which EU law guarantees him or her.

43      In the judgment of 19 June 2025, Lubreczlik (C‑396/24, EU:C:2025:460, paragraph 44), to which the referring court referred, the Court did not in any way rule in favour of either of the two theories in question. It held only that Article 7(1) of Directive 93/13 must be interpreted as precluding national case-law according to which, where a term of a loan agreement classified as unfair renders that agreement invalid, the seller or supplier is entitled to require the consumer to repay the full nominal amount of the loan obtained, irrespective of the value of repayments made by the consumer in performance of that agreement and irrespective of the amount remaining due.

44      The Court subsequently clarified that the principles established in the judgment of 19 June 2025, Lubreczlik (C‑396/24, EU:C:2025:460, paragraph 44), do not preclude an interpretation of the relevant rules of national law which makes it possible to arrive at a situation where, following a set-off at the initiative of the seller or supplier between its claim and the consumer’s claim, the respective amounts of which are not identical, only the party which remains the debtor of the amount not covered by its own claim against the other party is ordered to pay that amount to the latter (see, to that effect, judgment of 22 January 2026, Herchoski, C‑902/24, EU:C:2026:42, paragraphs 61 and 62). Therefore, in such a situation, the amount of the repayments made by the consumer in performance of the void agreement and the outstanding amount are indeed taken into account, with the result that that consumer is not required to repay the full nominal amount of the loan obtained.

45      In the present case, the referring court points out that the application of the balance theory requires the court to set off, of its own motion, the reciprocal claims of the parties. It clarifies that Polish law does not confer on it the power to effect such a set-off, since that law provides for the possibility of offsetting claims only at the initiative of a party, in compliance with certain conditions, in particular the creditor’s submission of a declaration of set-off.

46      In that regard, it follows from the case-law that, although the Member States are obliged to lay down in their national law procedural rules to ensure that the right to restitution guaranteed to consumers by Directive 93/13 is respected, it does not give rise, in principle, to an obligation to implement the right to restitution by means of offsetting to be carried out by the national court ex officio (see, to that effect, judgment of 30 June 2022, Profi Credit Bulgaria (Offsetting ex officio in the event of an unfair term), C‑170/21, EU:C:2022:518, paragraph 44).

47      It follows that the directive, without requiring the national court to set off ex officio the reciprocal claims of the consumer and the seller or supplier, does not, in principle, preclude that court from doing so, if its domestic law, including the need to comply with any procedural requirements that may be laid down by that law in relation to the set-off of claims, allows it to do so.

48      The referring court submits that the automatic set-off of reciprocal claims following a declaration that a contract is void on account of the unfair terms contained therein is likely to benefit the seller or supplier and have negative consequences for the consumer, with the result that it is liable to undermine the protection which that directive guarantees the consumer.

49      In the first place, according to that court, such set-off deprives the consumer of a large part of his or her claim and of the interest thereon, since a claim arises only if the consumer has repaid an amount exceeding that of the capital lent. Such a result would be contrary to the objective of that directive, which is to restore the consumer, by means of the restitutory effect, to the situation in which he or she would have been in the absence of unfair terms.

50      In that regard, it should be recalled that that objective must be pursued in compliance with the principle of proportionality, which is a general principle of EU law, which requires that the national legislation implementing that law does not go beyond what is necessary to achieve the objective pursued (see, to that effect, judgment of 16 April 2026, Jangielak, C‑752/24, EU:C:2026:307, paragraph 33 and the case-law cited).

51      That principle would be infringed if restitutio in integrum were to be excluded in respect of the seller or supplier. Accordingly, the obligation to restore the parties to their original position, following the invalidation of a loan agreement containing unfair terms, must be mutual; the seller or supplier may not, however, seek compensation from the consumer going beyond reimbursement of the capital paid in respect of the performance of that agreement containing unfair terms together with the payment of default interest at the statutory rate from the date on which notice is served (judgment of 16 April 2026, Jangielak, C‑752/24, EU:C:2026:307, paragraph 34 and the case-law cited).

52      Furthermore, the restitutory effect attached to the invalidation of a loan agreement containing unfair terms, which also justifies the action for restitution brought by the seller or supplier, must also ensure that the protection of the rights guaranteed by the legal order of the European Union does not entail the unjust enrichment of the consumer (judgment of 16 April 2026, Jangielak, C‑752/24, EU:C:2026:307, paragraph 35 and the case-law cited).

53      In the present case, it should be noted that the set-off of the reciprocal claims of the consumer and the seller or supplier gives rise to a right of restitution in favour of the party holding the highest claim, in an amount corresponding to the difference between those claims.

54      In order to guarantee the restitutory and dissuasive effects referred to in paragraphs 38 and 39 of the present judgment, the national court must ensure that the consumer has a right to default interest on the amount of the payments made by him or her under the contract which exceeds that of the capital lent.

55      Subject to verification by the referring court, this appears to be the case in the main proceedings, since it is apparent from the file before the Court that Bank accepts, in essence, that interest on the amount exceeding that of the capital lent is payable to the borrowers, from the day following the formal notice constituted by the attempt to reach an amicable settlement referred to in paragraph 13 of the present judgment.

56      In the second place, the referring court’s concern is that a set-off, carried out of the court’s own motion, between the reciprocal claims of the consumer and the seller or supplier would penalise the former on the ground that, as long as the capital lent has not been repaid, the seller or supplier could delay the legal proceedings and evade payment of the claim without suffering negative consequences.

57      In that context, it should be borne in mind that, according to the case-law, Article 6(1) and Article 7(1) of Directive 93/13 preclude a judicial interpretation of the law of a Member State according to which, following a declaration that a mortgage loan agreement is void, the bank has the right to seek from the consumer an amount going beyond reimbursement of the capital paid in respect of the performance of that agreement and payment of default interest at the statutory rate from the date on which notice is served. Subject to that reservation concerning default interest at the statutory rate, the bank is not entitled to receive remuneration for the use of that capital by the consumer (judgment of 22 January 2026, Herchoski, C‑902/24, EU:C:2026:42, paragraph 73 and the case-law cited).

58      Accordingly, a seller or supplier who seeks to delay legal proceedings for a declaration of invalidity of a loan agreement containing unfair terms would further extend the period during which the amount corresponding to the capital lent to the consumer would not yield any remuneration for that seller or supplier.

59      Consequently, the concern expressed by the referring court does not appear to be justified.

60      In the third place, that court points out that, by means of an ex officio set-off, the seller or supplier may recover the capital lent even after many years of inactivity, the risk of that seller or supplier’s claim being time-barred thus being eliminated.

61      In that regard, it must be pointed out that the very existence of the claims for restitution made by the consumer and the seller or supplier presupposes that the loan agreement concluded between them is invalid. Thus, as long as the validity of that contract is not called into question by the consumer, the seller or supplier does not have any claim for restitution that may become time-barred.

62      In the fourth place, the referring court mentions the risk that when the consumer has asked the bank to return all the payments made to it, he or she may be regarded, following a set-off carried out by the national court of its own motion between the reciprocal claims of that consumer and that bank, as having been unsuccessful in part and, accordingly, be ordered to pay the costs, or part of them.

63      The Court observes that, as the referring court essentially acknowledges, the set-off of claims makes it possible to prevent the seller or supplier from choosing to bring a separate action in order to assert his or her claim against the consumer, resulting in multiple proceedings and, therefore, in additional costs, which would not be in the consumer’s interest (see, to that effect, judgment of 22 January 2026, Herchoski, C‑902/24, EU:C:2026:42, paragraph 69).

64      In addition, it is settled case-law that award of the costs of judicial proceedings before the national courts falls within the procedural autonomy of the Member States, subject to compliance with the principles of equivalence and effectiveness (judgment of 27 November 2025, Gryczara, C‑746/24, EU:C:2025:925, paragraph 46 and the case-law cited).

65      Failing any reference to those principles by the referring court, only the principle of effectiveness appears to be relevant, in the present case, as regards costs.

66      In that connection, the Court has repeatedly held that although that principle does not preclude, in general, the consumer from incurring certain legal costs when he or she brings proceedings for a declaration that a contractual term is unfair, it should also be observed that Directive 93/13 confers on consumers the right to apply to a court to have a contractual term declared unfair and disapplied, a right the effectiveness of which must be preserved. Therefore, the rules on the award of costs in such proceedings must not deter consumers from exercising that right (judgments of 27 November 2025, Gryczara, C‑746/24, EU:C:2025:925, paragraph 48, and of 22 January 2026, Herchoski, C‑902/24, EU:C:2026:42, paragraph 78).

67      Moreover, it should be borne in mind that the principle that national law must be interpreted in conformity with EU law requires national courts, in observance, inter alia, of the prohibition on interpretation of national law contra legem, to do whatever lies within their jurisdiction, taking the whole body of domestic law into consideration and applying the interpretative methods recognised by domestic law, with a view to ensuring that the directive in question is fully effective and achieving an outcome consistent with the objective pursued by it (judgment of 22 January 2026, Herchoski, C‑902/24, EU:C:2026:42, paragraph 80 and the case-law cited).

68      In the present case, Bank submits that, under Polish law, if the consumer is successful in respect of the invalidation of a contract, the court may, even if it rejects part of the consumer’s claim for restitution, consider that the consumer has been successful and therefore that he or she must not pay the costs relating to the proceedings concerned.

69      It is ultimately for the referring court to examine whether the national legislation at issue in the main proceedings may be interpreted in conformity with Directive 93/13 and, if so, to draw the appropriate legal conclusions (judgment of 22 January 2026, Herchoski, C‑902/24, EU:C:2026:42, paragraph 82).

70      In particular, that court must ensure the effectiveness of the borrowers’ right to obtain a finding of invalidity in respect of the agreement at issue, containing unfair terms, and the restitution of the payments unduly received by Bank, by preventing the rules on the allocation of costs from deterring those borrowers from relying on the rights conferred on them by Directive 93/13.

71      In the fifth place, the referring court states that a mechanism for offsetting claims raises difficulties where the performance of the loan agreement has given rise to heterogeneous financial services, in particular, where the capital was lent in zlotys, but repayments were made in Swiss francs. Set-off in such a situation is impossible on the ground that, under Article 498 of the Civil Code, set-off is subject to the homogeneity of the reciprocal payments.

72      In that regard, Bank states that Polish law defines how sums of money expressed in foreign currencies must be converted into zlotys.

73      In addition, it should be borne in mind that, as is apparent from paragraph 12 of the present judgment, the borrowers, in respect of the performance of the agreement at issue, made payments to Bank partly in zlotys and partly in Swiss francs.

74      In those circumstances, it will be for the referring court, in accordance with the principle that national law must be interpreted in conformity with EU law as recalled in paragraph 67 of the present judgment, to assess whether national law allows it to guarantee the restitutory effect required by Directive 93/13, by a set-off of the reciprocal claims of the parties to the agreement which takes account of all the payments made by the borrowers.

75      In the sixth and last place, that court considers that any mechanism for the ex officio set-off of claims fails to have regard to the will of the consumer who, in most cases of a mortgage loan agreement being declared void, would request restitution of all payments made and would not choose to set off the amount of those payments against the capital lent. That court states that such set-off breaches the adversarial principle, which is binding on the court in particular when it decides a dispute on the basis of a plea in law raised ex officio.

76      In that connection, it should be borne in mind that, for the purposes of assessing the consequences for the consumer’s situation flowing from the invalidation of a contract as a whole, the intention expressed by the consumer is decisive. The system of protection envisaged by Directive 93/13 does not apply if the consumer objects to it. The consumer is entitled, after having been informed by the national court, not to assert the unfair and non-binding nature of a term, thus giving free and informed consent to the term in question and thereby avoiding the invalidation of the contract. In order for the consumer to be able to give free and informed consent, it is for the national court to indicate to the parties, in the context of national procedural rules and in the light of the principle of equity in civil proceedings, objectively and exhaustively the legal consequences which the removal of the unfair term may entail. Such information is, in particular, all the more important where non-application of the unfair term is liable to lead to the invalidation of the contract in its entirety, potentially exposing the consumer to claims for restitution (judgment of 22 January 2026, Herchoski, C‑902/24, EU:C:2026:42, paragraph 67 and the case-law cited).

77      Thus, if the national court intends to apply national law to the effect that that invalidation would result in the set-off of the court’s own motion of the respective claims for repayment of the parties to that contract, it is required to inform the consumer in advance, in order to enable him or her to express his or her intention in full knowledge of the facts as regards that invalidation.

78      Consequently, where the consumer, after having received information from the court having jurisdiction as to the consequences that are liable to follow from the invalidation of the loan agreement between him or her and the seller or supplier, decides not to challenge the invalidation of that agreement by that court, the fact that that court may, of its own motion, set off the reciprocal claims of the parties is not contrary either to the consumer’s intention or to the adversarial principle.

79      It follows from paragraphs 49 to 78 of the present judgment that none of the observations made by the referring court in relation to the mechanism enabling it to set off, of its own motion, the reciprocal claims of the parties to a contract following the invalidation of that contract on account of the unfair terms contained therein permits the inference that EU law precludes a national court from effecting such set-off, in compliance with the procedural requirements laid down by national law, which it is for that court to assess.

80      In the light of the foregoing, the answer to the questions referred is that Article 6(1) and Article 7(1) of Directive 93/13 must be interpreted as not precluding, in principle, a judicial interpretation of national law according to which the court seised by the consumer of a claim for repayment of amounts paid under a mortgage loan agreement, rendered invalid by the unfair terms contained therein, proceeds of its own motion to set off the reciprocal claims of the consumer and the seller or supplier who are parties to that agreement, with the result that the consumer is recognised as having a claim solely on the amount of the payments made in respect of the performance of that agreement which exceeds the amount of the capital lent and a right to default interest on that excess amount.

 Costs

81      Since these proceedings are, for the parties to the main proceedings, a step in the action pending before the referring court, the decision on costs is a matter for that court. Costs incurred in submitting observations to the Court, other than the costs of those parties, are not recoverable.

On those grounds, the Court (Ninth Chamber) hereby rules:

Article 6(1) and Article 7(1) of Council Directive 93/13/EEC of 5 April 1993 on unfair terms in consumer contracts

must be interpreted as not precluding, in principle, a judicial interpretation of national law according to which the court seised by the consumer of a claim for repayment of amounts paid under a mortgage loan agreement, rendered invalid by the unfair terms contained therein, proceeds of its own motion to set off the reciprocal claims of the consumer and the seller or supplier who are parties to that agreement, with the result that the consumer is recognised as having a claim solely on the amount of the payments made in respect of the performance of that agreement which exceeds the amount of the capital lent and a right to default interest on that excess amount.

[Signatures]

*      Language of the case: Polish.

i      The name of the present case is a fictitious name. It does not correspond to the real name of any party to the proceedings.