Who Audits Public Companies – France 2021

The Big Four accounting firms are collectively engaged in 55.5% of all French engagements, down 1.5 percentage points from the previous year. EY led the way with 16% of all engagements, followed by Deloitte with 15%. Mid-tier firm Mazars was third with 13% of all engagements, while PwC and KPMG round out the top five with 12% each.

France is unique because of its joint audit requirement that all public interest entities (PIEs) – which include publicly listed entities – must engage at least two independent accounting firms to perform an annual audit. Many cite this requirement as the reason France has a more diverse and competitive audit market than other countries.

2021 Auditor Market Share - France

CAC 40

The Big 4 continue to have a dominant role among the largest companies. Combined, the Big 4 audit 80% of CAC 40 engagements, led by EY with 26% of all engagements. Meanwhile, Mazars audits another 17% of CAC 40 engagements. The only other audit firm in the CAC 40 is Grant Thornton with two engagements.


Deloitte led with 19% of all engagements among the CAC Mid 60. In total, the Big 4 are engaged in 65% of all CAC Mid 60 engagements. Mazars is number three among the top 5 firms in this index, with 17% of the market. Twelve firms share the remaining 18% of CAC Mid 60 engagements, led by Grant Thornton with 6%.


The CAC Small index is much more diverse, with the Big 4 plus Mazars combining for just over half (51%) of all engagements. Sixty-four firms share the other 49% of engagements. Grant Thornton leads among smaller firms with 9% of CAC Small engagement.

Joint Audit Market Composition

One advantage of joint audits – which had been discussed, in a modified version, as a possible audit reform in the UK – is the ability to engage a larger firm with greater resources to conduct a quality audit and a smaller firm with fewer resources as the joint firm. In theory, this would create a more diverse market and allow smaller firms to learn from larger firms while still ensuring quality audits.

Joint Audit Composition

However, in France, which is the largest market in which we have a proxy for this theory, we see limited support. Among the CAC 40, less than half of joint audit engagements include a Big 4 firm and a non-Big 4 firm. As we saw above, France’s largest mid-tier firm Mazars audits most of the non-Big 4 engagements.

Among the CAC Next 20, the index is split. Half of the index engages two Big 4 firms, while the other half engages one Big 4 and one non-Big 4 firm. Among the half that engage both a Big 4 firm and a non-Big 4 firm, Mazars and Grant Thornton are the only two non-Big 4 firms engaged.

Among the CAC Mid 60, nearly 58% of companies engage a Big 4 firm and a non-Big 4 firm. Meanwhile, 5% engage multiple non-Big 4 firms. Nearly half of these non-Big 4 firm engagements also include the mid-tier firm Mazars.

Among the CAC Small, 91% engage at least one non-Big 4 firm. Additionally, over a quarter of CAC Small companies engage multiple non-Big 4 firms. This may be an indication that joint audits promote the use of smaller firms amongst small and mid-sized companies.

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