The locks may soon be changed on banking's global stage, if this week's rumours on bank capital requirements hold any weight.A Bloomberg article on the Financial Stability Board's G20 recommendation on capital levels said an FSB working document it obtained showed the basic requirement would be set at 16 per cent to 20 per cent of risk-weighted assets, but speculated this could swell to 21 to 25 per cent with additional buffers for the biggest banks. "These could go even higher if a bank then had to comply with a so-called countercyclical buffer set by its local regulator to tame credit booms," Bloomberg said.NAB's Global Markets Credit Research team agreed, writing yesterday that: "The 2.5 per cent capital conservation buffer and additional buffers for the largest banks would not be counted towards this amount [of 16 to 20 per cent], so in reality capital levels could be between 20 per cent and 25 per cent." "If accurate, the FSB clearly aims to achieve a high Total Loss Absorbency Capacity (TLAC) for Global Systemically Important Banks (GSIBs) with a high proportion of junior debt and other loss-absorbing instruments featuring," the NAB researchers wrote."Indeed nothing more senior than normal senior unsecured debt would be allowed to qualify."Australian Big Four banks currently hold total capital levels of around 12 per cent, NAB said."Although none are GSIBs, APRA and the Financial System Inquiry will be looking to take a significant lead from, if not slavish observance to, the FSB's recommendations in due course."We would like to stress at this stage that there remains little point trying to estimate an accurate end-state for bank capital, both globally and domestically with so many moving pieces at this stage," NAB concluded. The Australian reports that ANZ CEO Mike Smith (in an email to B20 colleagues including Westpac boss Gail Kelly, Standard Chartered chief executive Peter Sands, Societe Generale chief Frederic Oudea and Sumitomo Mitsui Financial Group chair Masayuki Oku) wrote of the Financial Stability Board's "comprehensive" acceptance of a review process to deal with any unintended, adverse ­effects in the real economy from post-crisis reforms.