On 7 September 2021, the European Central Bank (ECB) and the European Banking Authority (EBA) published a joint letter that they had sent to the European Commission regarding the EU implementation of the outstanding Basel III reforms. In the letter the ECB and EBA argue that it is “crucial to avoid implementation approaches that would be inconsistent with international agreements” and that this includes, but is not limited to, the implementation of the output floor. With regards to the output floor the ECB and EBA state that it should be implemented so that there is only one measure of risk-weighted assets per bank. They assert that introducing an additional set of requirements based on the output floor (the so-called “parallel stacks” approach) would deviate from the Basel standards, increase the complexity of the framework, and impair the comparability of capital ratios across banks and jurisdictions. They also add that it would undermine the effectiveness of bank specific supervisory capital requirements and the incentives those requirements create for banks to improve their risk profiles and risk management.