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Definition

Limited vs reasonable assurance for sustainability reporting

Limited assurance uses less extensive procedures and a negative-form conclusion, while reasonable assurance requires more persuasive evidence and supports a positive-form opinion on whether the sustainability information meets the stated criteria.

What are limited and reasonable assurance for sustainability reporting?

They are different levels of independent work on the same reported information and criteria. ASSA 5000 paragraphs 18(f) and 190(c)(vi) require limited assurance to use a negative-form conclusion about whether a material problem came to the provider's attention. Reasonable assurance uses a positive-form opinion that the information is prepared or presented, in all material respects, against the criteria.

Under the amended CSRD, Accounting Directive Article 34(1)(aa) requires a limited-assurance opinion where applicable. Directive (EU) 2026/470 removed the mandate for the Commission to adopt reasonable-assurance standards. Keslio's German reporting guide explains the amended CSRD and national implementation.

Why do assurance levels matter to you?

The level changes the work performed and the wording readers receive. In Australia, ASSA 5010 paragraph 7 equates a review with limited assurance and an audit with reasonable assurance; paragraph 10 phases those levels by reporting year.

How does the assurance work change?

ASSA 5000 paragraph 9 says limited procedures are less extensive. Paragraph A424 gives practical differences: fewer items or procedures, fewer site visits, and analysis based on broader trends. Reasonable assurance seeks more persuasive evidence and uses analysis precise enough to identify material errors.

What mistakes should you avoid?

  • Treating limited assurance as a fixed sampling percentage.
  • Calling a limited-assurance review an audit.
  • Leaving the level, criteria, disclosures, entity, or period unclear in the engagement terms.

Does limited assurance mean the information can be incomplete?

No. Both levels address material misstatement. Limited assurance means less extensive work and a different conclusion form, not a lower reporting obligation.

Can one report use both assurance levels?

Yes. ASSA 5000 paragraph A542 says the report should clearly separate which information received each level and the conclusion for each part.

Example

Hypothetical UAE facilities-services example: Suppose a company voluntarily commissions an ASSA 5000 engagement on two 2026 disclosures prepared under the GHG Protocol Corporate Standard: its Scope 1 and Scope 2 totals. Its file contains 12 monthly electricity reconciliations and seven refrigerant service reports, or 12 + 7 = 19 records.

Both proposals cover the same two disclosures, company, period, criteria, and 19-record file. The limited-assurance proposal uses staff enquiries, comparisons of monthly totals, and follow-up on unexpected movements. The reasonable-assurance proposal adds tests of source records and relevant controls to obtain more persuasive evidence. Its report gives a positive-form opinion; the limited report says whether a material problem came to the provider's attention.

The 19 records define the file, not a required sample or threshold. The provider chooses how many to test after assessing risk and evidence quality.

Where it comes up

Current CSRD limited-assurance opinion and removal of the reasonable-assurance standards mandateDirective (EU) 2026/470 recital 5; Audit Directive Article 26a(3); Accounting Directive Article 34(1), second subparagraph, point (aa)Australian review-to-audit progression for sustainability reportsASSA 5010 paragraphs 7 and 10(a)-10(c)Limited and reasonable assurance procedure and conclusion differencesASSA 5000 paragraphs 9, 18(f), 190(c)(vi), and A424

Related terms

Sustainability assurance

Sustainability assurance is an independent assessment of defined sustainability information against named criteria, ending in a report that states the provider's conclusion and level of assurance.

Corporate Sustainability Reporting Directive (CSRD)

The Corporate Sustainability Reporting Directive (CSRD) requires qualifying EU undertakings and groups, plus certain non-EU groups, to publish assured sustainability information under European Sustainability Reporting Standards (ESRS).

AASB S2 Climate-related Disclosures

AASB S2 Climate-related Disclosures sets the climate information that qualifying Australian entities must include in their statutory sustainability report, covering governance, strategy, risk management, metrics, targets, and greenhouse gas emissions.

Materiality

Materiality is the test a company uses to decide which sustainability topics matter enough to manage or report because they could affect its finances, reflect significant impacts on people or the environment, or both.

Sources

Last verified 2026-08-20

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Limited vs reasonable assurance for sustainability reporting Definition | Keslio