The theory:
Single Rulebook = CRR [Regulation 575/2013 directly applicable] + CRD IV [Directive 2013/36 must be transposed] + BRRD [2014/59] + DGSD [2014/49] + PSD2 [2015/2366] + AMLD + EBA RTS/ITS + EBA Guidelines.

Purpose per EBA: Provide a single set of harmonised prudential rules which institutions throughout EU must respect. Before, European banking legislation was based on Directives which left room for significant divergences, leading to different interpretations, legal uncertainty, enabling institutions to exploit loopholes.

The Spanish reality:
The denomination "single rulebook" is useful, it is not entirely accurate. There are implications resulting from retention of national discretions. Europe's banking market remains fragmented along national lines: a bank operating in Germany, Poland and Spain still faces three different supervisory reporting formats, three different consumer protection regimes and three different insolvency frameworks.

3 Mechanisms of Divergence in Spain

1. Regulation vs Directive:
CRR is Regulation - directly applicable. CRD IV is Directive - Spain must transpose via Law 10/2014 and Banco de España Circular 2/2014 of 31 January. Transposition creates divergence by delay and gold-plating.

Current Example - Spain infringement 2025:
European Commission is sending Spain to Court of Justice of EU for failing to transpose Directive EU 2024/1174 modifying MREL [minimum requirement for own funds and eligible liabilities for banks]. Commission says consequence is European banking market with unevenly applied rules. Spain missed deadline.

This is classic: Single Rulebook says MREL, but Spanish Law 11/2015 on recovery and resolution still reflects old MREL calibration.

2. National Discretions and Options :
Spanish Report from Asociación Española para el Derecho Financiero notes:[ONDs]

Main problem arising from single rulebook is lack of complete harmonisation, especially in regulation and directive concerning capital requirements. Main national discretions relate to capital - e.g. non-deduction from CET1 of financial stakes in insurance undertakings if...

Banco de España Circular 2/2014 exercises 30+ ONDs: e.g. treatment of deferred tax assets, transitional provisions for CET1, SME supporting factor. EBA Q&A 2013_206 and 2016_2735 on Collateral Received show differing interpretations by market participants.

3. EBA Q&A has no binding force:
EBA Single Rulebook Q&A tool launched to ensure consistent application. But EBA itself states: The Q&A have no binding force in law, nor are they subject to comply or explain process. So Spanish banks can interpret differently until CJEU decides.

Banco de España as national competent authority under PSD2 supervises payment providers, but can apply stricter standards. EBA Single Rulebook on Strong Customer Authentication confirms merchants may apply stricter authentication than regulatory minimum, which is precisely what Redsys [Spanish payment scheme] does. US cards fail on Renfe because Redsys requires 3DS v2.2 while EBA minimum is v2.1 - interpretative divergence in action.

Spain's 4 Big Divergences That Became Case Law

This is where Single Rulebook collides with Spanish consumer sovereignty under Constitution Art 51.

DIVERGENCE 1: CONSUMER PROTECTION - FLOOR CLAUSES [Cláusulas Suelo]

EU Rule: Directive 93/13/EEC on unfair terms - clause must be transparent.

Spanish Interpretation Divergence:
Tribunal Supremo Judgment May 9, 2013: Floor clauses establishing minimum interest [e.g. 3% when Euribor 0.5%] are abusive for lack of transparency, but Supreme Court limited retroactivity to May 2013 to protect banks' solvency.

CJEU Correction:
Joined Cases C-154/15, C-307/15, C-308/15 - Gutiérrez Naranjo - Dec 21, 2016:
CJEU held Spanish case law establishing time limit for purposes of nullity of floor clause is incompatible with EU law. Solution given by Tribunal Supremo supposes incomplete and insufficient protection for consumers, and therefore contrary to EU law. Retroactivity must be full, from inception of mortgage.

Result: Tribunal Supremo Judgement No. 419/2017 of 4 July had to change criteria on procedural costs in light of EU judgment. This is textbook interpretative divergence: Spanish Supreme Court tried to balance banking stability [Single Rulebook prudential goal] vs consumer protection [national constitutional goal], CJEU said consumer protection wins.

Cost to Spanish banking sector: ~ €4-5 bn returned.

DIVERGENCE 2: IRPH INDEX - OFFICIAL BUT NOT TRANSPARENT?

EU Rule: Art 1(2) of Directive 93/13: clauses reflecting mandatory legal/regulatory provisions excluded from unfairness review.

Spanish Bank Argument: IRPH [Indice de Referencia de Préstamos Hipotecarios] is official index published by Banco de España, regulated by Spanish law, therefore cannot be reviewed.

Divergent National Case Law:

• Tribunal Supremo STS 669/2017 Dec 14: IRPH clauses not subject to transparency control because legal index.
• First Instance Court Barcelona No.38 referred to CJEU.

CJEU Interpretations:

C-125/18 - Gómez del Moral Guasch v Bankia SA - March 3, 2020 - Grand Chamber:
Declares clause setting benchmark index based on mortgage loans of savings banks is included in scope of Directive on unfair terms. Not excluded.

C-265/22 and C-300/23 - Dec 12, 2024:
CJEU categorical: fact that index is official and public does not exempt bank from obligation to inform customer in clear and understandable manner.

Spanish Supreme Court Plenary Judgments 1590/2025 and 1591/2025 - Nov 11, 2025:
Analyze validity of IRPH clause in light of CJEU July 13, 2023 and Dec 12, 2024. Held clause that references interest to IRPH is clause that defines main object of contract, subject to transparency control. Must pass double control of incorporation and transparency.

Over 1 million mortgages in Spain affected. This is the biggest Single Rulebook divergence in mortgage law: EBA/ECB view IRPH as compliant prudential reference, CJEU/Spanish courts view as potentially abusive consumer practice.

DIVERGENCE 3: PSD2 / SCA - REDSYS GOLD-PLATING

EU Rule: EBA Single Rulebook Q&A on SCA - minimum requirements.

Spanish Practice:
Banco de España allows Redsys to apply stricter authentication. Result: cross-border divergence - French or US cards declined on Spanish merchants.

No CJEU case yet, but under discussion as fragmentation of Single Market.

DIVERGENCE 4: RESOLUTION - MREL TRANSPOSITION

EU Rule: BRRD 2014/59 as amended by 2024/1174 - MREL calibration.

Spanish Divergence:
Spain has not transposed. Commission infringement. If a Spanish bank like Banco Sabadell has merger conditions contested by Commission as contravening EU single market principles, ECB and EBA as supervisors must apply different MREL during interim.

This shows Single Rulebook requires national law, but if national law late, you have two rulebooks.

Why Spain Diverges More Than Others - Legal Reason

Spain operates under dual supervisory model:

• Significant banks [Santander, BBVA, CaixaBank]: Direct ECB supervision under SSM, applying CRR directly + Banco de España Circular 2/2014 for options.
• Less significant: Banco de España direct.

Plus:

• Banco de España Circular 2/2016 on accounting
• CNMV Circular 2/2020 on advertising of investment products - adds sustainability disclosure beyond SFDR.

EBA 2024-2025 focus is strengthening Single Rulebook and embedding DORA and MiCA to reduce this divergence. New AMLR Regulation EU 2024/1624 is Regulation, not Directive, precisely to eliminate legal fragmentation by creating Single Rulebook - organizations can no longer rely on local interpretations.

Bottom line for Spain:
Single Rulebook aims for one prudential language. Spanish courts add a second language - constitutional consumer protection. The divergence is resolved only when CJEU overrules Tribunal Supremo, which it has done twice [floor clauses 2016, IRPH 2020/2024]. Until then, Spanish banking lives with two interpretations: what is prudent for ECB and what is fair for Spanish consumer.