Reasonable assurance is a high level of assurance regarding material misstatements, but not an absolute one. Reasonable assurance includes the understanding that there is a remote likelihood that material misstatements will not be prevented or detected on a timely basis. To achieve reasonable assurance, the auditor needs to obtain sufficient appropriate audit evidence to reduce audit risk to an acceptably low level. This means that there is some uncertainty arising from the use of sampling, since it is possible that a material misstatement will be missed.
When conducting an audit of financial statements, the high-level objectives of the auditor include obtaining reasonable assurance as to whether a client’s financial statements are free from material misstatement, thereby allowing the auditor to express an opinion on whether the financial statements are presented fairly, in all material respects, in accordance with the applicable financial reporting framework (such as generally accepted accounting principles).