CSRD Assurance Providers
CSRD requires third-party limited assurance from your first reporting year. Quality assurance providers are heavily booked. Understanding who can provide assurance, what they check, and how to select the right partner is critical — and urgent.
CSRD requires third-party limited assurance from your first reporting year. Statutory auditors (the Big Four and national audit firms) are automatically accredited for CSRD assurance in most EU member states.
Who is accredited to provide CSRD assurance
Statutory auditors (the Big Four and national audit firms) are automatically accredited for CSRD assurance in most EU member states. However, being accredited does not mean having the capacity or expertise to deliver quality sustainability assurance.
Independent Sustainability Assurance Providers (ISAPs) — specialist firms such as Bureau Veritas, SGS, LRQA, DNV, and ERM — are accredited separately and often have deeper sustainability expertise. They conduct ISO 14001 and other sustainability certifications, giving them domain knowledge audit firms lack.
The choice between audit firm and ISAP depends on: existing audit relationship, price sensitivity, sector-specific expertise needs, and whether the national regulator has a preference.
What to look for when selecting a provider
Sector experience: Has the provider assured CSRD reports in your sector? ESRS E1 climate disclosures for a manufacturing company require different expertise than ESRS S2 supply chain disclosures for a retailer.
ESRS taxonomy expertise: Can the provider assess XBRL tagging accuracy? Few providers have developed this capability for the first generation of CSRD reports.
Capacity: Can they commit to your timeline? With 50,000+ companies eventually needing assurance, capacity is finite. Providers are already booking 2027 and 2028 engagements.
Price and scope: Get proposals from at least 3 providers. Scope should specify exactly which standards and datapoints are covered, and the level of testing procedures.
Preparing your data for assurance
The single most common assurance finding is inadequate documentation — numbers are right but the trail from source data to disclosed figure is unclear. Build documentation into your process from day one.
For each disclosed datapoint, maintain: the source data; the calculation methodology; the emission factor source and version; the internal review and approval record; and any estimates or assumptions made.
Assurers will sample test a selection of datapoints — typically 20–30% of quantitative disclosures. Any sampled datapoint must be fully traceable. ESGMaster maintains an automated audit trail for every calculation.
Frequently asked questions
Can we use a different assurance provider from our financial auditor?
Yes — CSRD does not require the same firm for financial and sustainability assurance. Many companies use their financial auditor for sustainability assurance for relationship convenience, but specialist ISAPs often provide better value.
What is a limited assurance engagement procedure?
Limited assurance involves enquiry and analytical procedures — reviewing your processes, comparing disclosed figures to underlying records, and checking for inconsistencies. It does not involve the extensive transaction testing of a financial audit (reasonable assurance).
What if we cannot find an assurance provider in time?
File a report explaining the circumstances and the steps taken. This will still attract regulatory scrutiny but is better than filing an unassured report without explanation. Engage immediately — do not wait.