The jurisprudential fluctuations concerning the validity of the irph reference index in mortgage credit agreements

Abstract

Credit secured by a mortgage is typically long-term financing and is subject to an interest rate determined by reference to a benchmark index. Among such indices is the Mortgage Loan Reference Index (IRPH), which began to be used in Spain in the 1990s. Although it has largely fallen into disuse and has been replaced in most cases by the EURIBOR, its continued applicability in many mortgage loan agreements —given their long duration—has given rise to extensive case law concerning its validity, comprehensibility, and its classification as an unfair term due to a lack of transparency. This article provides a critical review of the relevant jurisprudence and analyses the most recent judgments of the Spanish Supreme Court of 2025, which establish binding doctrine on the definitive validity of the IRPH as an index for determining remunerative interest in mortgage loan agreements.