Key takeaways
- The Dutch audit market splits between six OOB firms and approximately 224 reguliere vergunninghouders, with dual supervision from the AFM (statutory audits) and the NBA's Raad voor Toezicht (other assurance work).
- Non-Big 4 firms captured disproportionate growth, moving from 18% to 40% market share of non-PIE statutory audit revenue between 2014 and 2024.
- The SRA represents over 370 firms (approximately 70% of reguliere vergunninghouders) and provides standardised methodology, but is not a regulator.
- The Wijzigingswet accountancysector introduces quality reporting obligations and enhanced governance requirements that will eventually reach non-Big 4 firms.
How the Dutch audit market is structured
The Netherlands has two categories of audit firm licence. OOB-accountantsorganisaties (currently six firms: Deloitte, EY, KPMG, PwC, BDO, and Mazars) hold licences to audit public interest entities. Reguliere vergunninghouders hold AFM licences to perform statutory audits of non-PIE entities. As of 2024, there are approximately 224 reguliere vergunninghouders, though this number has been declining gradually as smaller firms merge or exit.
The distinction matters because it determines your supervision regime. OOB firms face direct, continuous AFM inspection of individual audit files. Reguliere vergunninghouders face AFM supervision for statutory audit work but fall under the NBA's Raad voor Toezicht for non-statutory assurance, compilation, and review engagements.
Below the AFM-licensed tier sits a much larger group: accountancy practices that perform no statutory audits but carry out compilation engagements, voluntary reviews, and other assurance work. These firms hold no AFM licence and fall exclusively under the NBA's six-yearly toetsing cycle.
Statutory audit thresholds
Dutch thresholds (as of financial year 2024) require an audit when a company meets at least two of: assets exceeding €7.5 million, net turnover exceeding €15 million, or more than 50 employees, on two consecutive balance sheet dates. These thresholds were increased by 25% in March 2024, meaning some previously audit-obligated companies now fall below the threshold.
The numbers: what the AFM reports about non-Big 4 growth
The AFM's Sector in Beeld 2025 report provides the clearest picture. Total statutory audit revenue for non-PIE clients grew from €678 million in 2014 to €1,485 million in 2024. Reguliere vergunninghouders captured a disproportionate share of that growth, moving from 18% to 40% market share.
54% of statutory audits performed by reguliere vergunninghouders are now fully data-driven (gegevensgericht). This number has been increasing steadily. For firms considering technology investment, more than half of competitors are already there.
Incident reporting tells a more complicated story. In 2024, the AFM received 56 incident notifications: 18 from OOB firms and 38 from reguliere vergunninghouders. Whether the increase from 27 in 2023 reflects more incidents or better reporting discipline is unclear.
Fraud risk identification varies by firm size. Small reguliere vergunninghouders have the lowest percentage of statutory audits with more than two identified fraud risks. At OOB firms, the share of audits identifying more than two fraud risks rose from 42% in 2023 to 47% in 2024.
Who regulates what: AFM, NBA, and the SRA's role
The AFM supervises all firms holding a Wta licence for their statutory audit work. Its supervision is risk-based and thematic, not file-by-file every year.
The NBA's Raad voor Toezicht supervises quality for non-statutory work: voluntary audits, review engagements, compilation engagements under NV COS 4410, and other assurance work. This is the six-yearly toetsing cycle with its new mid-cycle development conversation. In 2024, the Raad reviewed 183 firms and found a 76% pass rate.
The SRA is not a regulator. It is a network organisation representing over 370 independent SME-focused accounting and audit firms. Approximately 70% of all reguliere vergunninghouders are SRA members. The organisation provides quality programmes, model handbooks, peer review services, and collective lobbying. It is also accredited by the NBA to conduct quality reviews, creating a tension where it represents the firms it simultaneously reviews on the NBA's behalf.
The service organisation model
Most mid-tier and smaller audit firms subscribe to a service organisation (serviceorganisatie) that provides standardised audit methodologies, quality handbooks, template files, and ongoing technical support. The major service organisations include Novak, Auxilium, Fiscount, and Extendum.
In 2024, 54% of non-PIE audit firms used professional practice support from the SRA, up from 45% in 2021. An additional 20% used support directly from the NBA. Independent quality infrastructure is the exception, not the norm.
Service organisation membership typically costs between €5,000 and €15,000 annually depending on firm size. A failed NBA review triggers improvement plan costs that run significantly higher, plus the reputational and operational disruption of a re-review cycle.
Worked example: how supervision plays out for Bakker & Partners
Scenario: Bakker & Partners Accountants B.V. is a seven-partner firm in Utrecht with €3.2M revenue. Four partners hold RA qualifications. The firm performs 45 statutory audits per year (non-PIE), plus approximately 120 compilation engagements and 15 voluntary reviews. It holds an AFM Wta licence and is an SRA member.
AFM supervision (statutory audit work)
The AFM requires annual data submission through the market monitor. In 2024, the firm reported two early terminations and one incident notification. The AFM's thematic investigation on fraud risk results in a questionnaire documenting how fraud risks are identified across sample statutory audit files.
NBA Raad voor Toezicht (non-statutory work)
Bakker & Partners was last reviewed in 2021 and received a pass with recommendations. Under toezicht op nieuwe leest, the firm had its first development conversation in March 2024. No formal findings resulted. The next full toetsing is scheduled for 2027.
SRA membership
The firm uses SRA's standardised audit methodology and quality handbook. When the AFM's fraud risk report was published, the SRA organised a session with member firms and announced updates to practical guidelines and work programmes.
Upcoming regulatory changes for non-Big 4 firms
The Wijzigingswet accountancysector introduces several changes. Quality reporting through audit quality indicators (AQIs) will initially apply only to OOB firms. The reporting obligation for reguliere vergunninghouders will not be introduced until after a three-year evaluation.
Enhanced internal governance requirements will apply to the 15 to 20 largest reguliere vergunninghouders. These firms will need to establish or strengthen internal supervisory structures. For mid-tier firms below this threshold, the requirement does not apply directly, but the Raad voor Toezicht may incorporate governance questions into its review process.
Private equity involvement is a growing concern. The market share of non-PIE firms with PE investment rose from 11% in 2023 to approximately 30% by 2025. Both the Raad and the AFM will scrutinise PE-backed arrangements for pressure on fee levels, growth-over-quality incentives, and governance structures where decision-making may not rest with qualified accountants.
Where CSRD fits for non-Big 4 firms
The CSRD creates both opportunity and risk. Large non-PIE entities coming into CSRD scope from 2025 onwards will need sustainability assurance, and not all will seek this from their current Big 4 auditor. But performing sustainability assurance requires competencies most non-Big 4 firms have not yet built.
Firms that position early for CSRD assurance work in the non-PIE segment may capture a growing market. Firms that take on sustainability assurance without adequate expertise will face regulatory scrutiny from the AFM.
Practical checklist for understanding your firm's regulatory position
- Confirm which supervisory bodies have jurisdiction over your firm: AFM (if Wta-licensed), NBA Raad voor Toezicht (for other work), or both. Map each engagement type to its supervisor.
- Check your SRA membership status. If you are among the 46% of non-PIE firms not using SRA support, evaluate whether your internal quality infrastructure is sufficient.
- Review the AFM's Sector in Beeld 2025 report for your firm's size category. Know how your metrics compare.
- Assess whether the raised statutory audit thresholds have affected your audit client portfolio.
- If your firm has received or is considering PE investment, review the Raad's 2024 comments on PE involvement and prepare governance documentation.
Common mistakes
- Assuming AFM supervision and NBA review cover the same ground. The AFM supervises statutory audit work. The NBA reviews non-statutory assurance and compilation work. A firm holding a Wta licence that also performs compilations answers to two different supervisors for two different categories of engagement.
- Treating the SRA's role as regulatory. The SRA provides support and represents member interests, but it does not set standards or grant licences. When SRA guidelines conflict with NVKS or Wta requirements, the regulatory standard prevails.
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Frequently asked questions
How is the Dutch audit market structured?
Six OOB firms hold licences for public interest entity audits. Approximately 224 reguliere vergunninghouders hold AFM licences for non-PIE statutory audits. Below these sit practices performing no statutory audits that fall exclusively under the NBA's review cycle.
What is the SRA's role in the Dutch audit market?
The SRA is a voluntary network organisation representing over 370 firms, approximately 70% of reguliere vergunninghouders. It provides quality programmes, model handbooks, and peer review services but is not a regulator. It is also accredited by the NBA to conduct quality reviews.
What share of statutory audit revenue do non-Big 4 firms hold?
Non-Big 4 firms now hold a 40% share of non-PIE statutory audit revenue, up from 18% in 2014. They perform roughly 60% of all statutory audits. Total non-PIE statutory audit revenue grew from 678 million to 1,485 million euros over the same period.
What regulatory changes are coming for non-Big 4 firms?
The Wijzigingswet introduces quality reporting through audit quality indicators (initially OOB firms only), enhanced governance requirements for the 15-20 largest reguliere vergunninghouders, and increased scrutiny of private equity involvement. The CSRD also creates both opportunity and risk for sustainability assurance work.
Further reading and source references
- AFM Sector in Beeld 2025: Comprehensive data on the Dutch statutory audit market including non-PIE firm metrics, market share trends, and supervisory findings.
- Raad voor Toezicht Annual Report 2024: NBA quality review pass rates, recurring deficiencies, and private equity commentary.
- Wijzigingswet accountancysector: Legislative reform bill introducing AQIs and enhanced governance for audit firms.
- NBA Quality Review: Preparation Guide: Companion post on preparing for the Raad voor Toezicht's toetsing cycle.