The European Central Bank published an Occasional Paper reviewing how country-specific Additional Credit Claims (ACC) frameworks were used to broaden eligible collateral for Eurosystem refinancing operations in non-standard periods, and drawing lessons for future collateral policy discussions. The paper, which reflects the authors’ views, concludes that while ACCs were introduced as a crisis instrument, experience since 2012 shows they can support monetary policy implementation if paired with appropriate risk controls. The study documents the evolution of ACC frameworks across euro area national central banks, from their introduction during the sovereign debt crisis, through major expansion during the pandemic, to gradual phasing-out since 2022. It reports that ACCs’ share of banks’ collateral pools ranged from 2% in early 2012 to 19% in the first quarter of 2023, with use peaking during the pandemic and declining thereafter. Using panel data, it finds ACC usage was highly concentrated, with 90% of ACC collateral between 2012 and 2024 attributable to 42 banks, yet pledging ACCs was not systematically associated with more concentrated overall collateral pools. ACC users were mainly universal banks and diversified lenders of varying size, and ACC use is correlated with higher short-term secured funding costs, with unclear causality. Substitution between ACCs and marketable instruments such as asset-backed securities and covered bonds was generally limited, except in a French case where phasing out residential mortgage ACC pools was associated with increased holdings of retained residential mortgage-backed securities and own-used covered bonds. The paper links its findings to the Eurosystem’s ongoing collateral framework changes described in the study, including the discontinuation of several ACC components and a further step in 2024 to discontinue many remaining elements expected to be implemented by end-2025, alongside work to integrate certain temporary measures into the general collateral framework, notably acceptance of national central banks’ statistical in-house credit assessment systems under a harmonised framework and preparatory work to allow pools of loans to non-financial corporations.