The euribor today, July 24, 2026, rises to 2.993% and brings the average of July closer to 2.83%

The monthly average of the euribor used as the official reference index in Spain is calculated, first, from the daily values of the euribor index set at the European level and, then, it becomes an official rate when the Bank of Spain publishes it monthly in the BOE and on its website. Normatively, the euribor at one week, one month, three, six, and twelve months is recognized as an official interest rate in Order EHA/2899/2011 and in Bank of Spain Circular 5/2012, amended by Circular 1/2021. In variable-rate mortgages, contracts usually link the rate to that official euribor index (usually the 12-month one) plus a spread and provide for periodic reviews (annual or more frequent), but the exact timing and reference month are set in each deed. No further normative detail is available, in the sources consulted, about which specific month should be taken for each review: that is determined by the contract.

Calculation of the euribor and monthly average

Origin of the euribor index

The euribor is a crucial reference index in European financial markets. Bank of Spain Circular 5/2012, dated June 27, in its annex 8 (amended by Circular 1/2021), defines the euribor at one week, one month, three months, six months, and one year as official reference indices. It indicates that the euribor appears in the annex of Implementing Regulation (EU) 2016/1368, which includes it among the “critical benchmark indices” according to Regulation (EU) 2016/1011.

According to this Circular, for each term (including twelve months):

• It is defined as the simple arithmetic monthly average of the daily values of the euribor reference index.
• These averages are calculated by the European Money Markets Institute (EMMI) and published on its website or by any other dissemination means.
• In case of absence of publication by EMMI, the Bank of Spain will calculate and publish these monthly averages.

That is, the prior technical procedure consists of: daily obtaining of the euribor (based on interbank euro quotations) and calculation of a monthly average for each term, including the twelve-month one, which is the one usually used in mortgages.

Conversion into an official index in Spain

Legal recognition as an official interest rate

Order EHA/2899/2011, on transparency and protection of banking service customers, establishes what are considered official interest rates. In its article 27.1 (according to the consulted excerpt) it expressly includes:

• The euribor at one week, one month, three months, six months, and one year as one of the official reference indices for the mortgage market.

The same Order provides that:

• Official interest rates will be published monthly by the Bank of Spain in the “Official State Gazette” (BOE) and will also be available on its electronic headquarters.

Bank of Spain Circular 5/2012, issued in development of that Order and available in the BOE as Circular 5/2012, includes the list of official indices and their detailed technical definition, including the euribor and the monthly average rule calculated by EMMI, with subsidiary intervention by the Bank of Spain. This Circular was amended, particularly in annex 8, by Circular 1/2021.

Official publication

Based on Order EHA/2899/2011 (Order EHA/2899/2011) and Circular 5/2012, the scheme is:

• EMMI calculates and disseminates the monthly averages of the euribor.
• The Bank of Spain takes those data and converts them into official reference rates, publishing them monthly in the BOE and on its website.
• That publication in the BOE is what grants the status of official reference index of the mortgage market.

In parallel, the regulation maintains a similar treatment for the historical Mibor (one-year interbank market) in mortgages prior to 2000, but always under the same logic: technical definition of the index and monthly publication by the Bank of Spain in the BOE (see Order of December 1, 1999, and its development and Order EHA/2899/2011 itself).

Use of the monthly average of the euribor in mortgage reviews

Linking to the euribor as an official index

Circular 5/2012 expressly describes euro loans with variable rates linked to the official euribor reference index through a predetermined spread, with long terms (equal to or greater than twenty years) and review of the rate “annually or in periods more…” (the consulted text is cut off, but it reflects reviews at least annually). This confirms that, in the market practice foreseen by the supervisor, variable-rate mortgages are referenced to the official euribor and are reviewed at least annually.

However, in the sources used, there is no single legal rule imposing on all mortgages which specific month of euribor must be applied in each review (for example, “average of the previous month” or another formula). That detail is contractually articulated in each loan deed, with the regulation limited to:

• Defining the euribor and other references as official indices and guaranteeing their monthly publication by the Bank of Spain.
• Requiring transparency: the deed and pre-contractual documentation must clearly identify the applicable official index (article 27 of Order EHA/2899/2011 and development in Circular 5/2012).

Therefore, the normative procedure can be summarized as follows: the monthly average of the euribor is calculated from daily data; EMMI disseminates it; the Bank of Spain incorporates it as an official interest rate and publishes it monthly in the BOE and on its website; and each mortgage contract sets how and when it takes that official rate (usually the 12-month euribor) in the agreed periodic reviews. No further information is available in the consulted sources about a general obligation to use a specific month for all mortgages.

The Bank of Spain does not set or calculate the euribor, but it does have a relevant role in its supervision from the prudential and conduct perspective of Spanish entities that use it or contribute to its calculation. The index is mainly regulated at the European level, but the Bank of Spain acts as the national supervisory authority over banks participating in the calculation panel and over the use of the euribor in contracts with clients. Its central function is to ensure that Spanish entities comply with European rules on reference indices and that the use of the euribor is transparent and appropriate for consumers.

What is the euribor and who administers it

The euribor is a reference interest rate massively used in Spain, especially in variable-rate mortgages. It is a European index: it is obtained from the rates at which a panel of banks would lend money to each other in the interbank market. Its administrator is a European body (not the Bank of Spain), subject to the European Benchmark Regulation (known as BMR).

Direct supervision of the euribor administrator falls on a competent authority of another Member State and European institutions. Therefore, the Bank of Spain does not decide the methodology, calculation formula, or the daily value of the index, which are determined within the European framework.

Supervision of entities contributing to the euribor

The Bank of Spain's first major competence regarding the euribor is the supervision of Spanish banks that are part of the contributing entities panel to the index. These entities send their interest rate data to the administrator for euribor calculation.

In this area, the Bank of Spain:

• Supervises the internal governance and control systems of entities submitting data, to prevent manipulation or conflicts of interest.
• Reviews that there are adequate internal policies and procedures for the preparation and transmission of quotes to the euribor administrator.
• Controls, within prudential supervision, that the contribution to the index is not used to unduly influence the market or obtain illicit competitive advantages.
• Cooperates with European supervisory authorities when investigating incidents or possible irregularities related to contributions from Spanish entities.

Supervision of the use of the euribor in contracts with clients

The second block of the Bank of Spain's powers refers to how Spanish financial entities use the euribor in their products, especially in mortgage loans and other credits referenced to this index.

In this field, the Bank of Spain:

• Monitors compliance with transparency and banking customer protection regulations when marketing products linked to the euribor.
• Analyzes that pre-contractual and contractual information about the functioning of the euribor, its variability, and its risks is clear, sufficient, and understandable.
• Supervises interest rate review clauses, substitute indices, and the treatment of scenarios of sharp euribor increases or decreases.
• Controls the correct application of European and Spanish regulation on reference indices in financial contracts, including the obligation to provide alternative indices if the euribor ceased to be published.

Macroprudential, statistical, and market surveillance role

Beyond the direct relationship with entities, the Bank of Spain uses its analytical capacity to monitor the impact of the euribor on the Spanish economy:

• It produces statistics and studies on the exposure of households and companies to euribor variation, very relevant in a country with a high percentage of variable-rate mortgages.
• It assesses financial stability risks derived from sharp euribor movements (delinquency, banking solvency, household financial burden).
• It may issue recommendations or warnings in its reports and memos when it detects vulnerabilities associated with the index's evolution.

What the Bank of Spain does not do regarding the euribor

It is also important to underline what is outside its powers:

• It does not calculate or publish the euribor.
• It does not decide the calculation formula, the transaction sample, or the detailed methodology of the index.
• It cannot discretionarily intervene to modify the euribor value, since it is governed by a European framework and interbank market activity.

In summary, the Bank of Spain acts as supervisor of Spanish entities that contribute to and use the euribor and as an analyst of the index's impact on the financial system and clients, within a regulatory and supervisory scheme that is predominantly European.

In a variable mortgage in Spain, the entity can only update the interest rate if it limits itself to applying the formula stated in the contract (official reference index + spread) and complies with transparency and consumer protection regulations. The review must be based on an objective and public index (such as the euribor) and carried out with the agreed periodicity, without the bank being able to unilaterally modify the spread or introduce new limits. Additionally, the entity must inform the client of each review and the new applicable rate, complying with prior information standards and control of abusive clauses (floor, ceiling, rounding, etc.). If the official index ceases to be published, it can only be replaced according to what is legally or contractually foreseen, never at discretion.

Basic legal framework

The update of the rate of a variable mortgage is framed within the general regime of protection of financial consumers and mortgage contracting. The core is in:

• Real estate credit contracts law, which strengthens transparency in home mortgages and sets rules on interest rates, commissions, and floor/ceiling clauses.
• Banking transparency regulations, including the Order on transparency and protection of banking service customers and Bank of Spain circulars, which regulate pre-contractual information, reference indices, and advertising.
• Consumer and user regulations and case law on abusive clauses, especially from the Supreme Court and the CJEU regarding mortgages.

Reference index and calculation formula

To be able to review the interest rate, the contract must clearly include:

• The reference index (for example, 12-month euribor or other official indices supervised by the Bank of Spain).
• The fixed spread added to (or subtracted from) the index.
• The periodicity of the reviews (semiannual, annual, etc.).

The law requires that indices be objective, public, and verifiable, and regularly published by an authority (usually the Bank of Spain or official reference systems). The entity cannot unilaterally change either the index or the spread; to do so would require a novation with client consent and notarial formalization.

Transparency and prior information

Before signing, the entity must provide the client with standardized documentation (such as pre-contractual and personalized information sheets) explaining:

• That the rate is variable and how it is calculated.
• Examples of rate increase and decrease scenarios, including the effect of possible floor/ceiling clauses.
• Total costs, APR, and risks derived from interest variability.

The notary must verify that the client has received that information sufficiently in advance and understands the functioning of the variable rate, recording a material transparency certificate in cases where the law requires it.

Form and deadlines for notification of reviews

Once the loan is in force, each rate review must strictly follow the agreed formula. Practice and transparency regulations require that the entity:

• Calculate the new rate on the review date taking the latest official data of the published index.
• Communicate to the client the updated rate, the new installment, and the application date, through statements, correspondence, or digital channels.
• Include clearly the interest breakdown in periodic statements.

The review occurs by operation of the contract: the client does not need to sign anything new if only the agreed formula is applied. If the margin, commissions, or any other element of the interest rate is to be modified, a novation agreed upon, usually by public deed, is necessary.

Floor/ceiling clauses, rounding, and abusiveness

Clauses setting a floor (minimum rate) or a ceiling (maximum rate) are valid only if they have been negotiated and explained with material transparency. Case law has declared many floor clauses null due to insufficient information or contradiction with advertising. In practice, banks must:

• Highlight separately and visibly the existence of the floor/ceiling.
• Offer simulations showing how those limits operate in different scenarios.

Regarding rounding of the rate, Bank of Spain regulations and supervision have restricted those roundings always upwards that systematically place the client in a worse position. Any rounding rule must be objective, balanced, and understandable; otherwise, it may be considered abusive.

If the official index ceases to be published

Financial regulations foresee that, if an index ceases to exist or is seriously altered, official substitute indices may be set. Contracts usually include a substitution clause expressly referring to that alternative index. If the reference disappears and there is no clear contractual provision, the problem cannot be resolved by unilateral bank decision but through agreement with the client or according to a specific legal rule determining the substitution. In any case, judicial control against possible abusive changes is maintained.