On 20 January 2026, the PRA published PS1/26, finalising Basel 3.1 rules and related policy materials. The package largely confirms the near-final policy, with minor clarifications. This article provides an overview of the final rules. This article provides an overview of the final UK Basel 3.1 rules.

Liquidity stress testing remains a cornerstone of effective risk management and regulatory compliance for banks. However, a persistent challenge lies in interpreting what constitutes a “severe but plausible” stress scenario, particularly in the context of evolving depositor behaviours and increasing digitalisation of banking.

This paper aims to address this challenge by examining how stress scenarios can be robustly calibrated using empirical evidence backed by statistical methods, with particular focus on liquidity stress testing informing the Internal Liquidity Adequacy Assessment Process (ILAAP).