Audit risk is the risk that the auditor will suffer financial and/or reputational loss as a result of doing something wrong or omitting to do something during an audit engagement. All audits, therefore, involve risk. There is always the possibility of fraud or error remaining undetected no matter how careful an auditor is in gathering and assessing audit evidence in support of the auditor's resulting opinion. It is possible that the auditor will arrive at an unsuitable opinion. A large part of an audit engagement is dealing with this risk - assessing it at the start of the engagement, and gathering evidence and reassessing it during the engagement.