28. For banks, ECL is a complex accounting estimate that has high inherent risk, which means it is highly susceptible to material misstatement [High inherent risk refers to "the susceptibility of an assertion about a class of transaction, account balance or disclosure to a misstatement that could be material, either individually or when aggregated with other misstatements, before consideration of any related controls", ISA 200, Overall objectives of the independent auditor and the conduct of an audit in accordance with international standards on auditing, paragraph 13(n).]. ROMM is a key concept in external audit as it determines the extent of audit evidence required and influences the audit approach that will allow the external auditor to express an opinion on a bank's financial statements. It is important that the external auditor correctly identify significant ROMMs given the requirement to test the design and implementation of the corresponding relevant controls [ISA 540 (Revised), Auditing Accounting Estimates and Related Disclosures, paragraph 19.].