Basel IV Compliance Guide: CRR3, Output Floor & RWA Changes by Jurisdiction

Basel IV is already in force in the EU. If your institution uses internal models for credit, market, or operational risk, the output floor is now constraining your RWA calculations — even in 2025, at just 50% of the standardised floor. The full 72.5% arrives by 2030, and the intermediate steps will require ongoing capital planning adjustments.

This guide covers what Basel IV actually changes, how the rules differ across the EU, UK, and US, and what compliance teams need to monitor as implementation unfolds.

What Is Basel IV? The Naming Confusion Explained

The Basel Committee on Banking Supervision (BCBS) never used the term "Basel IV." The BCBS calls the package of reforms finalized in December 2017 the "finalisation of Basel III." The "Basel IV" label emerged from industry — primarily from European banks who viewed the reforms as substantial enough to constitute an entirely new framework.

The distinction matters because regulators and official publications use "Basel III" terminology. When the EBA publishes an impact assessment of "Basel III final reforms," that's what practitioners call Basel IV. When the PRA implements "Basel 3.1," same reforms.

The core problem Basel IV addresses: two banks with identical risk exposures can produce dramatically different RWA numbers by using different internal models. This made capital ratios incomparable across institutions and gave banks with sophisticated modelling teams a capital advantage unrelated to their actual risk management quality. Basel IV constrains this through the output floor and through tighter constraints on model inputs.

The Output Floor: The Central Change

The output floor is the headline change of Basel IV. It establishes that a bank's risk-weighted assets calculated using internal models (the IRB approach for credit risk, IMA for market risk) cannot fall below 72.5% of what the standardised approaches would produce.

In practice: if your standardised approach produces RWAs of €100 billion, your internal model RWAs must be at least €72.5 billion — regardless of what your models say. Banks whose models produce lower RWAs than the floor will see their capital requirements increase.

The phase-in schedule in the EU (CRR3):

The EBA estimates that the output floor will increase aggregate EU bank RWAs by approximately 18.5% once fully phased in, with significant variation by institution. Banks with highly optimized internal models in low-risk portfolios (mortgage lending, for example) will feel the impact most acutely.

"The output floor doesn't punish good risk management — it prevents the modelling arms race where competitive pressure pushed banks to produce ever-lower RWA estimates. The floor creates a baseline below which no model can go, regardless of how sophisticated it is."

FRTB: Market Risk Overhaul

The Fundamental Review of the Trading Book (FRTB) replaces the old Internal Models Approach (IMA) for market risk with a restructured framework that includes both a revised standardised approach (SA-TB) and a new IMA.

Under the old IMA, banks calculated market risk capital using value-at-risk (VaR) models — an approach that proved inadequate during the 2008 financial crisis. FRTB replaces VaR with Expected Shortfall (ES), uses a 97.5% confidence level (vs. 99% VaR), and incorporates a stressed calibration period.

The new IMA under FRTB is desk-level rather than firm-wide: each trading desk must qualify separately for model approval. Desks that fail to meet supervisory standards fall back to the standardised approach (SA-TB). This creates a more granular and potentially more volatile capital picture.

Key FRTB implications for compliance teams:

• P&L attribution testing — Desks using the IMA must demonstrate that their risk model accurately explains actual P&L. Failing the test triggers a switch to SA-TB, typically at higher capital cost.
• Backtesting requirements — Daily backtesting at both desk and firm level, with escalating capital add-ons for frequent exceptions.
• Data requirements — FRTB requires significantly more granular risk factor data, with specific requirements around risk factor observability.
• Trading/banking book boundary — FRTB tightens the criteria for book assignment, limiting opportunities to move assets between books for capital benefit.

Operational Risk: The SMA Replaces AMA

Basel IV replaces the Advanced Measurement Approach (AMA) for operational risk capital with the Standardised Measurement Approach (SMA). The AMA was intended to allow sophisticated banks to use internal models for operational risk — in practice, it produced highly variable results and was widely criticised for lacking comparability.

The SMA uses a single standardised formula combining two components:

• Business Indicator (BI): A measure of bank size and business activity based on income statement items (interest, leases, dividends, trading, and fee-based activities). Larger banks have higher BI coefficients.
• Loss Component: For large banks (BI above €1 billion), 10 years of internal loss data feeds into the capital calculation. Better loss history reduces capital; worse history increases it.

One controversial feature of the SMA: unlike the AMA, it cannot produce lower capital requirements than the standardised approach — only higher ones for banks with poor loss histories. This has been criticised as creating a perverse incentive to under-report operational losses.

Implementation by Jurisdiction

European Union: CRR3 and CRD6

The EU implemented Basel IV through the Capital Requirements Regulation 3 (CRR3) and Capital Requirements Directive 6 (CRD6), published in the Official Journal in June 2024. CRR3 is directly applicable from January 1, 2025, with the output floor phase-in running through 2030.

The EU implementation includes several deviations from the BCBS standards — areas where the EU chose a different approach than the international baseline:

• SME supporting factor: The EU retained its preferential treatment for SME loans, which the BCBS did not include in its standards. This reduces the capital cost of lending to small businesses below what a pure Basel implementation would require.
• Infrastructure supporting factor: Similar preferential treatment for qualifying infrastructure loans.
• Real estate: CRR3 introduced more granular risk weights for residential and commercial real estate, with specific treatment for income-producing real estate (IPRE).
• ESG risk: CRD6 introduced new requirements for banks to assess and manage environmental, social, and governance risks — going beyond the BCBS standards.

The EBA has a substantial mandate to produce regulatory technical standards and guidelines under CRR3. Many of these are still being published through 2026, meaning the full technical detail of EU implementation continues to evolve.

United Kingdom: Basel 3.1

The UK PRA published its near-final rules for Basel 3.1 (the UK's terminology for Basel IV) in September 2024, with implementation beginning January 1, 2026. The PRA's implementation broadly follows the BCBS standards, with some UK-specific adjustments.

Key UK Basel 3.1 features:

• Output floor applies from January 1, 2026, phasing to 72.5% by 2030 (same phase-in as the EU)
• The PRA chose not to adopt the EU SME and infrastructure supporting factors — UK banks face higher capital requirements for these asset classes than EU peers
• FRTB applies to UK trading book positions
• The PRA published a transitional regime for the output floor's interaction with Pillar 2A, to prevent double-counting of risks

UK firms also face the challenge of post-Brexit divergence: UK Basel 3.1 and EU CRR3 differ in detail, creating complexity for banks with significant operations in both jurisdictions.

United States: Basel III Endgame (Delayed)

US implementation of Basel IV remains the major outstanding question in global banking regulation. The US agencies (Federal Reserve, OCC, and FDIC) published a joint notice of proposed rulemaking (NPR) for the "Basel III Endgame" in July 2023. The proposal attracted significant industry opposition, with banks arguing the capital increases were too large and the standardised approaches too conservative.

As of 2026, the US has not finalized the rule. The change in administration in January 2025 introduced significant uncertainty about the final shape of US implementation. The current regulatory direction suggests a substantially revised reproposal, likely with a reduced capital impact and potential exemptions for regional banks below certain asset thresholds.

US banks should not assume the 2023 NPR will be finalized as proposed — but should also not assume it will be abandoned entirely. The international pressure from BCBS peer review (which will evaluate US compliance with the Basel standards) creates some floor on how far the US can deviate from the global framework.

What Compliance Teams Need to Do Now

For EU-regulated institutions, Basel IV (CRR3) is not a future project — it's current regulatory reality. For UK institutions, the first phase applies from January 2026. For US institutions, monitoring the reproposal is the priority.

Capital planning: The output floor phase-in requires multi-year capital planning. At 50% in 2025, the constraint may not yet bite for most institutions — but by 2027 (60%) and certainly by 2030 (72.5%), the impact on capital ratios for model-reliant banks will be substantial. Boards need capital projections that incorporate the full floor trajectory.

RWA recalculation: Both the SA-TB and the new credit risk standardised approach under CRR3 use different risk weight schedules than the previous rules. Institutions need to have recalculated RWAs under the new framework, not just modelled the output floor impact on old calculations.

FRTB infrastructure: Banks using IMA for market risk need desk-level model approval processes, P&L attribution testing, and the enhanced data infrastructure FRTB requires. Many banks are implementing FRTB in parallel with CRR3, creating significant simultaneous demand on risk and technology teams.

EBA technical standards pipeline: The EBA continues to publish CRR3 technical standards through 2026. Compliance teams need a mechanism to track these publications — missing an RTS that changes a calculation methodology has direct capital consequences.