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Levels of assurance explained

 

The objective of an assurance engagement is to obtain sufficient appropriate evidence to express a conclusion, providing reasonable or limited assurance, as to whether the audited body has complied with the specified requirements of the appropriate legislation (the ‘criteria’) in all material respects.

The higher the level of assurance provided, the greater the confidence the individual can place in the matter being assured. However, for an audit team leader to provide a higher level of assurance, they need to reduce the risk that a material misstatement exists in the matter being audited. The audit team leader achieves this by conducting a more in-depth and rigorous assessment of the matter being audited.

Absolute assurance means that there is no assurance risk. Reducing assurance risk to zero is very rarely attainable or cost beneficial; primarily because the evidence available to an audit team leader is persuasive rather than conclusive, and audit team leaders are required to use judgement in gathering and evaluating assurance evidence. As such, absolute assurance is not part of the NGER Audit Determination.

The NGER Audit Determination’s definition of a reasonable assurance engagement is as follows: 'A reasonable assurance engagement means an assurance engagement in which the audit team leader gives an opinion, expressed as a reasonable assurance conclusion, if appropriate in the circumstances of the engagement'.

Because the level of assurance obtained in a limited assurance engagement is lower than in a reasonable assurance engagement, the procedures the assurance practitioner will perform in a limited assurance engagement will differ from, and are narrower in scope than those performed in a reasonable assurance engagement.

The primary differences between reasonable assurance engagements and limited assurance engagements, in terms of the way the assurance practitioner addresses the assessed risks of material misstatement and the procedures they use, are as follows:

  • The emphasis placed on the nature of various procedures:
    The emphasis placed on the nature of various procedures as a source of evidence will likely differ, depending on the engagement circumstances. For example:
    • the assurance practitioner may judge it to be appropriate in the circumstances of a particular limited assurance engagement to place relatively greater emphasis on enquiries of the entity’s personnel and analytical procedures; and relatively less emphasis, if any, on tests of controls and obtaining evidence from external sources than would be the case for a reasonable assurance engagement
    • where the entity uses continuous measuring equipment to quantify emissions flows, in a limited assurance engagement the assurance practitioner may decide to respond to an assessed risk of material misstatement by enquiring about how often the equipment is calibrated. In the same circumstances, in a reasonable assurance engagement the assurance practitioner may decide to examine the entity’s records of the equipment’s calibration or independently test its calibration, or
    • where the entity burns coal, in a reasonable assurance engagement the assurance practitioner may decide to independently analyse the characteristics of the coal. In a limited assurance engagement, the assurance practitioner may decide that reviewing the entity’s records of laboratory test results is an adequate response to an assessed risk of material misstatement.
  • The extent of further procedures:
    Further procedures are performed to a lesser extent in a limited assurance engagement than in a reasonable assurance engagement. This may involve:
    • reducing the number of items to be examined, for example, reducing sample sizes for tests of details
    • performing fewer procedures (for example, performing only analytical procedures in circumstances when, in a reasonable assurance engagement, both analytical procedures and tests of detail would be performed), or
    • performing procedures on location at fewer facilities.
  • The nature of analytical procedures:
    In a reasonable assurance engagement, analytical procedures performed in response to assessed risks of material misstatement involve developing expectations of quantities or ratios that are sufficiently precise to identify material misstatements. In a limited assurance engagement, on the other hand, analytical procedures are often designed to support expectations regarding the direction of trends, relationships and ratios rather than to identify misstatements with the level of precision expected in a reasonable assurance engagement.

When significant fluctuations, relationships or differences are identified, appropriate evidence in a limited assurance engagement may often be obtained by making enquiries of the entity and considering responses received in the light of known engagement circumstances, without obtaining additional evidence.

In addition, when undertaking analytical procedures in a limited assurance engagement, the assurance practitioner may, for example:

  • use data that is more highly aggregated; for example, data at a regional level rather than at a facility level, or monthly data rather than weekly data, or
  • use data that has not been subjected to separate procedures to test its reliability to the same extent as it would have been for a reasonable assurance engagement.

5.1.1 Addressing a change in risks when issues are identified

During either a reasonable assurance or limited assurance engagement, the audit team leader's assessment of the risk of material misstatement in the subject matter may change during the course of the engagement. If the auditor becomes aware of a matter or matters that cause the auditor to believe that the risks of a subject matter being materially misstated has changed, the auditor shall design and perform additional procedures to obtain further evidence until the auditor is able to:

  • conclude that the matter is not likely to cause the subject matter to be materially misstated, or
  • determine that the matter(s) cause the subject matter to be materially misstated.

This requirement is the same for both a reasonable assurance and limited assurance engagement. ASAE 3000 provides further guidance on how auditors may deal with changes in risks and the need for additional procedures.

The NGER Audit Determination definition of a reasonable assurance engagement is: 'an assurance engagement in which the audit team leader gives an opinion, expressed as a reasonable assurance conclusion, if appropriate in the circumstances of the engagement'.

The table below outlines the differences between the procedures for a reasonable and a limited assurance engagement:

Type of engagementObjectiveEvidence gathering proceduresThe assurance engagement report
Reasonable assurance engagementA reduction in assurance engagement risk to an acceptably low level in the circumstances of the assurance engagement, as the basis for a positive form of expression of the auditor’s conclusion. Reasonable assurance means a high but not absolute level of assurance.

Sufficient appropriate evidence is obtained as part of a systematic assurance engagement process that includes:

  • obtaining an understanding of the assurance engagement circumstances
  • assessing risks
  • responding to assessed risks
  • performing further evidence gathering procedures, and
  • evaluating the evidence obtained.
Description of the assurance engagement circumstances, and a positive form of expression of the conclusion.
Limited assurance engagementA reduction in assurance engagement risk to a level that is acceptable in the circumstances of the assurance engagement but where that risk is greater than for a reasonable assurance engagement, as the basis for a negative form of expression of the auditor’s conclusion.Sufficient appropriate evidence is obtained as part of a systematic assurance engagement process that includes obtaining an understanding of the matter to be audited and other assurance engagement circumstances; but evidence gathering procedures are deliberately limited in comparison with a reasonable assurance engagement.Description of the assurance engagement circumstances, and a negative form of expression of the conclusion.

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