The UK Prudential Regulation Authority (PRA) has published discussion paper DP1/25 inviting views on potential reforms to the internal ratings based (IRB) approach to credit risk for residential mortgage exposures. The PRA recognises that medium-sized firms face challenges in developing compliant models for loss given default (LGD) and probability of default (PD), which may restrict access to the IRB framework and limit competition. To address this, the PRA is considering a new foundation IRB (FIRB) approach under which firms would model PD while applying fixed supervisory values for LGD and exposure at default (EAD). This would provide a proportionate alternative to the standardised approach (SA) and advanced IRB (AIRB) for firms with limited data or modelling capabilities. In parallel, the PRA is also exploring policy options to ease implementation of PD modelling requirements. These include revising or removing the 30% cyclicality calibration cap, simplifying long-run average default rate estimation and exploring through-the-cycle (TtC) models for medium-sized firms. The PRA is not committing to any policy changes at this stage but seeks views by 31 October. Any changes would take effect after the implementation of the near-final Basel 3.1 rules.
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