Banks that provide asset "custody" as part of an investment services business will have to meet new financial requirements outlined on Friday by the Australian Securities and Investments Commission.Under the changes, custodians and asset-holders will be required to hold net tangible assets amounting to the greater of A$10 million or 10 per cent of average revenue.The $10 million floor is double the current minimum.As rationale for the increase, ASIC said: "The substantial increase in the amount of assets under custody over the past two decades is closely correlated to the introduction of compulsory superannuation in the early 1990s."It also said: "The introduction of a 10 per cent of average revenue requirement for responsible entities (including asset holders for registered schemes) recognises the non-linear nature of operating risk.""The growth and anticipated further growth of assets under custody is particularly relevant to the risk of loss resulting from inadequate or failed internal processes, people and systems, or from external events."Banks potentially affected by the change include National Australia Bank, JP Morgan, BNP Paribas, Citi, State Street, and HSBC. These five, along with Northern Trust, account for 90 per cent of the market. "The custodial industry in Australia is concentrated so that the failure of even one major custodian could have a negative impact on a large number of AFS licensees and their clients, as well as confidence in the sector overall," ASIC said.BNY Mellon, Macquarie Bank and Royal Bank of Canada are three more banks with minor market shares.ASIC said it lacked financial data on custodians and could not assess how they currently met their financial requirements, nor could it assess the impact of the proposed requirements.