A company-by-company look at the audit firms behind Japan’s Nikkei 225, including Big Four market share, auditor tenure and the latest disclosed audit fees.
The Nikkei 225 is one of the most closely watched measures of Japan’s stock market, bringing together 225 companies listed on the Tokyo Stock Exchange.
Its composition changed on 1 October 2026, when JX Advanced Metals, Kokusai Electric and Capcom entered the index, replacing Konica Minolta, Archion and Kanadevia. The changes were part of Nikkei’s annual periodic review.
Big4News has identified the external auditor of every company in the updated index, together with the first financial year of the current audit relationship where this could be established and the latest disclosed audit fee.
The table below can be sorted by company, sector, auditor, tenure and audit fee.
Data checked as of 1 October 2026. Audit fees are shown in Japanese yen.
Nikkei 225 Audit Market Share
The Big Four audit 218 of the 225 companies
The audit market at the top of corporate Japan is highly concentrated.
KPMG audits 78 Nikkei 225 companies, giving it the largest share of the index at 34.7%.
EY follows with 67 companies, or 29.8%, while Deloitte audits 54, or 24.0%. PwC has a considerably smaller presence with 19 companies, or 8.4%.
Only seven companies use an auditor outside the Big Four.
Together, Deloitte, EY, KPMG and PwC therefore audit 218 of the 225 companies — 96.9% of the index.
That result closely matches the picture identified by Japan’s audit regulator. The Certified Public Accountants and Auditing Oversight Board reported that the Big Four global networks audited 97% of Nikkei 225 companies as of 31 March 2025. (CPAAOB 2025 Monitoring Report)
KPMG has the largest share
KPMG’s 78 mandates put it more than ten companies ahead of EY and give the firm more than one-third of the entire index.
Its clients span almost every major part of corporate Japan, from Panasonic and Honda to Sumitomo Mitsui Financial Group, Japan Post Holdings and East Japan Railway.
EY is particularly prominent among major industrial, chemical and financial groups, while Deloitte has a substantial presence among banks, trading companies and large diversified groups.
PwC’s market share is much smaller by number of companies, but several of its engagements are among the largest and most complex in the index, including Toyota Motor, Tokio Marine, Sony and Kyocera.
Just seven companies are not audited by the Big Four
The non-Big Four segment of the Nikkei 225 is small but more varied than in some other major markets.
Grant Thornton audits two companies: Baycurrent and Tokuyama.
Five other firms each hold one Nikkei 225 mandate:
UHY — Pan Pacific International Holdings
Yaesu Audit Corporation — Nissan Chemical
Gyosei & Co. — Comsys Holdings
Toyo Audit Corporation — Okuma
Ark LLC — Dai Nippon Printing.
That leaves non-Big Four firms with just 3.1% of the index.
Yet the picture across the broader Japanese listed-company market is less concentrated.
The CPAAOB reports that large audit firms’ share of domestic listed-company engagements fell from 67.5% in FY2020 to 58.1% in FY2024, while the share held by small and medium-sized firms increased from 18.4% to 25.9% over the same period. (CPAAOB 2025 Monitoring Report)
Smaller firms are gaining ground across Japan’s listed market as a whole, but the very largest companies remain overwhelmingly with the Big Four.
Some auditor relationships stretch back more than 70 years
Japan also stands out for the length of many audit relationships.
Big4News was able to establish an exact starting year for 156 of the 225 current engagements. Of those, 25 date to 1970 or earlier.
The oldest verified relationships in the dataset date to 1951.
EY’s audit lineages at Nichirei, Shin-Etsu Chemical and Eneos all trace back to that year. Nissan Motor and Nissui follow from 1953, while Shionogi dates to 1960 and PwC’s relationship with Nintendo to 1962.
A decades-long relationship does not necessarily mean that the present audit corporation existed under its current name throughout the period. Japanese disclosures can treat predecessor firms and audit-corporation reorganisations as part of one continuous audit relationship.
The Since field therefore records the first financial year of the continuous external-audit relationship supported by the issuer’s disclosure rather than implying that the present legal entity has existed unchanged since that date.
Japan rotates audit partners rather than imposing routine firm rotation
These long relationships are possible because Japan’s independence framework focuses heavily on the rotation of the individuals leading the audit rather than requiring companies to replace their audit firm after a fixed term.
JICPA states that individual CPAs and engagement partners on relevant listed-company audits must generally rotate at least every seven years, followed by a two-year cooling-off period.
For large audit corporations auditing 100 or more listed companies, lead engagement partners and engagement quality-control review partners are subject to a stricter five-year rotation and five-year cooling-off period. (JICPA)
This creates a different model from the mandatory audit-firm rotation rules that apply to public-interest entities in the European Union.
The firm may remain in place for decades while the partners responsible for leading and reviewing the engagement rotate.
The index changed on 1 October
The October periodic review brought three new companies into the Nikkei 225.
JX Advanced Metals is audited by EY. Big4News traces the continuous audit relationship to FY2003, and the latest identified audit remuneration is ¥544 million.
Kokusai Electric is also audited by EY, with the current relationship dating to FY2019 and an audit fee of ¥152 million.
Capcom is audited by KPMG. Its continuous engagement dates to FY2013, with latest identified audit remuneration of ¥147 million.
They replaced Konica Minolta, Archion and Kanadevia.
The net effect on Big Four market share was small, but it shifted the balance between the firms: EY gained two index companies, while KPMG’s total fell from 80 to 78.
There are also several recent auditor changes
Despite the prevalence of very long relationships, the market is not static.
KPMG became auditor of Kikkoman for FY2026, while PwC took over at Suzuki Motor. Deloitte became auditor of Shift for FY2026.
There are also appointments taking effect for FY2027. KPMG is the incoming auditor at Murata Manufacturing, while Deloitte is the incoming auditor at Fujikura. In both cases, the most recently disclosed fee still belongs to the predecessor firm, so the table identifies that explicitly rather than attributing the old fee to the incoming auditor.
That distinction is important when comparing recent auditor changes across the database.
SoftBank has the largest audit fee in the index
Audit-fee data is available for all 225 companies in the updated dataset.
The median identified audit fee is approximately ¥671 million.
The largest belongs to SoftBank Group, at ¥11.026 billion.
It is followed by:
Mitsubishi UFJ Financial Group — ¥9.808 billion
Toyota Motor — ¥8.780 billion
Tokio Marine Holdings — ¥8.403 billion
Sumitomo Mitsui Financial Group — ¥7.882 billion
NTT — ¥7.542 billion
Hitachi — ¥7.155 billion
Mitsubishi Corporation — ¥6.885 billion
Mizuho Financial Group — ¥6.832 billion
Sony Group — ¥6.749 billion
The size of the largest fees reflects the scale and complexity of these groups, many of which have extensive international operations and large networks of subsidiaries.
About the data
Auditor identifies the external accounting auditor for each Nikkei 225 constituent at the 1 October 2026 snapshot date. Big Four Japanese member firms are grouped under Deloitte, EY, KPMG or PwC for market-share purposes.
Since means the first financial year for which the current audit firm held the external audit engagement. Where an issuer discloses a precise continuous tenure rather than a starting year, Big4News may calculate the first financial year using inclusive counting.
Where predecessor audit firms or reorganisations are clearly included by the issuer in the continuous relationship, that continuity is preserved.
Audit fee is the latest safely attributable audit-service remuneration identified in the company’s disclosure. For Japanese companies this generally combines audit remuneration paid to the Japanese audit firm with audit remuneration paid to firms in the same network. Non-audit remuneration is excluded.
Where a recently appointed auditor has not yet audited a financial year and the latest disclosed fee belongs to the predecessor, the table says so explicitly.
Unsupported tenure dates are left blank rather than estimated.
Data checked as of 1 October 2026.
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