Basel IV Risk Management: What the New Capital Framework Means for Lending, Models, and Unrated Exposures
Implementation is unfolding unevenly, and the divergence between jurisdictions goes well beyond timing:
- Canada completed most requirements by early 2024.
- The EU went live with CRR III on January 1, 2025.
- The UK PRA finalized Basel 3.1 rules in January 2026, with implementation effective 1 January 2027.
- US agencies issued new capital proposals on 19 March 2026, with comments due 18 June 2026.
In the US, the 2026 proposals would materially reshape and simplify the capital framework for large banks, but the rules are not final and should not yet be considered settled.
The US and non-US frameworks are currently diverging in important respects, with the US framework still under proposal. European and UK banks face an output floor that constrains IRB benefits and increases capital requirements. US banks face the opposite: the agencies describe the March 2026 proposals as producing a modest aggregate decrease in capital requirements for large banks and a moderate decrease for smaller banks. Non-US final rules may still change pending what the US ultimately adopts.
The consequences cut across lending pricing, model validation, and portfolio construction, and they differ depending on where a bank’s exposures are booked.
How the Output Floor Reshapes Capital Allocation
The output floor is the mechanism by which Basel IV constrains the benefits of internal models at the portfolio level. It applies in the EU (live since January 2025), the UK (expected January 2027), and most non-US jurisdictions.
Under the current US proposals, the output floor as structured in the EU and UK framework does not apply in the same form. The Collins Amendment already makes standardized capital binding for US banks, and the 2026 proposals continue in that direction.
For EU and UK banks, two things matter most: the arithmetic of the floor itself, and how IRB constraints compound its impact on the exposures where internal models historically delivered the largest capital advantage.
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