When CBIZ entered the public markets in 1996, it began an institutional experiment that would eventually make it one of the most unusual organisations in professional services. The listed company developed a commercial platform around independently owned CPA firms, allowing it to provide accounting, tax, advisory, technology and administrative services while the regulated firms retained responsibility for attest work. Long before private equity became a major force in accounting, CBIZ had demonstrated that institutional capital and regulated professional ownership could coexist within the same economic system. (CBIZ – Corporate History and Frequently Asked Questions)
Public ownership gave CBIZ permanent capital, acquisition currency and liquidity for sellers. It enabled the company to consolidate businesses that might otherwise have remained distributed across hundreds of local firms, while giving investors access to the economics surrounding a regulated profession they could not own directly. The structure was not free of tension, but for decades it offered a workable accommodation between the capital requirements of a consolidator and the professional-ownership rules governing audit firms.
The acquisition of Marcum in 2024 appeared to validate the model at unprecedented scale. The approximately $2.3 billion transaction brought roughly $1.2 billion of annual revenue, more than 3,500 professionals and one of the largest public-company audit practices outside the Big Four. CBIZ expected to pay approximately $1.1 billion in cash, issue around 14.4 million shares and fund the transaction through a committed credit facility of up to $2 billion. The acquisition combined listed shares, substantial new debt and the credibility of a public company to complete a transaction that would have been difficult for most traditional partnerships to finance. (CBIZ – Marcum Acquisition Form 8-K and Transaction Materials)
Less than two years later, Grant Thornton Advisors agreed to acquire CBIZ in a transaction valuing the company at approximately $5 billion. The deal does not prove that public ownership had failed, nor does the available evidence establish that auditor-independence constraints caused the CBIZ board to sell. The official rationale emphasises shareholder value, scale, technology, industry expertise and international reach. The transaction nevertheless raises a more difficult institutional question. Public ownership had helped CBIZ build one of the largest professional-services platforms outside the Big Four, but Marcum expanded the regulated audit perimeter, increased the organisation’s financing requirements and intensified the interaction between the listed company and the professional firms surrounding it. The possibility raised by the sale is not that the public model stopped working, but that the institution it created became progressively harder to operate within the assumptions of that model. (Grant Thornton Advisors, New Mountain Capital and CBIZ – $5 Billion Transaction Announcement)
The Public Company That Became Harder to Keep Public
CBIZ’s ownership model separated economic ownership from professional responsibility. The listed company owned the employees, technology, offices, client-support infrastructure and commercial businesses surrounding the audit practice, while independently owned CPA firms retained responsibility for attest work and the professional judgements attached to it. That separation allowed CBIZ to access public capital without violating the ownership rules governing licensed accounting firms. (CBIZ – 2024 Annual Report and Form 10-K)
The legal boundary did not insulate the wider organisation from audit regulation. For independence purposes, CBIZ and its associated CPA firms were treated as connected parts of the same institution. Certain services, financial interests and commercial relationships were restricted across the platform, while SEC-reporting audit clients of the associated CPA firms could not own shares in CBIZ. These limitations had existed for years and were constraints the model could absorb while the audit practice remained a relatively contained part of the wider organisation.
Marcum changed the practical reach of those restrictions. The acquisition brought one of the largest portfolios of public-company audit clients outside the Big Four into the associated CPA structure and expanded the relationships across which independence had to be tested. CBIZ subsequently disclosed that conflicts created by the transaction required certain services to be terminated, resulting in revenue that could no longer be retained. The filing does not claim that these losses threatened the company’s viability or caused it to seek a buyer, but it shows that every expansion of the audit platform enlarged the exclusion zone surrounding the commercial business. (CBIZ – 2025 Annual Report and Form 10-K)
The capital markets offered an ambiguous verdict on that transformation. CBIZ shares closed 19.3 per cent lower on the day the Marcum transaction was announced. Two years later, Grant Thornton’s offer of $55 per share represented approximately a 54 per cent premium to CBIZ’s 30-day volume-weighted average price, but remained far below the $88.65 the shares had reached in early 2025. None of those numbers proves that CBIZ could no longer remain public. They reveal a widening gap between the strategic scale the company had created and the value the market was prepared to assign to it. CBIZ had not become an unsuccessful public company. It had become a more leveraged, regulated and institutionally complex one whose value was increasingly difficult to interpret through the conventional expectations of a listed professional-services business. (Financial Times – CBIZ to Buy SPAC-Focused Marcum in $2.3 Billion Accounting Deal; Financial Times – Grant Thornton Seals Accounting Sector’s Largest Takeover in a Generation)
The Audit Firm Grant Thornton Is Not Buying
The transaction is commonly described as Grant Thornton’s acquisition of CBIZ, one of the largest accounting firms in the United States. Legally, the buyer is acquiring CBIZ Inc., the listed commercial company, not the independent CPA firms that issue audit opinions. Those firms are separate legal entities with their own governing bodies and officers. They are owned by licensed CPAs, most of whom are employed by CBIZ subsidiaries, but CBIZ itself holds no ownership interest in them. (CBIZ – 2025 Annual Report and Form 10-K)
The distinction is not a technical footnote added to satisfy professional regulation. It is the institutional boundary that allows capital ownership and professional responsibility to sit within the same economic system without formally becoming the same organisation. Grant Thornton is buying one side of that boundary. The regulated firms, and the professional authority required to issue audit opinions, remain on the other.
The Marcum transaction demonstrates how deliberately that boundary is maintained. Before the sale closed, Marcum transferred substantially all of its non-attest assets and liabilities into Marcum Advisory Group. A CBIZ subsidiary then merged with that company, bringing advisory, tax and other commercial operations into the listed group. In a separate transaction, CBIZ CPAs purchased substantially all of Marcum’s attest assets. What was presented to clients and the market as one integrated accounting platform was therefore created through two legally distinct transactions: one involving the public company and another involving the independently owned professional firm. Grant Thornton inherits that architecture, but it does not erase it. (CBIZ – Definitive Proxy Statement for the Marcum Acquisition; CBIZ – First-Quarter 2026 Form 10-Q)
What changes ownership is the economic infrastructure surrounding the audit practice. CBIZ supplies professional staff, office management, marketing, premises, equipment, systems support and administrative services to the associated CPA firms in return for fees. It bears much of the commercial responsibility for workforce deployment, technology investment and operating efficiency, but its service agreements do not give it control over the CPA firms or the conduct of their attest work. Grant Thornton is therefore acquiring an unusually valuable but incomplete form of control: ownership of much of the platform through which the professional institution operates, without ownership of the firms responsible for its most regulated judgements. The transaction transfers the economics surrounding audit while preserving the separation on which audit legitimacy depends. (CBIZ – First-Quarter 2025 Form 10-Q)
Marcum Changed More Than the Size of CBIZ
The Marcum transaction was designed not merely to transfer ownership, but to keep the selling partners economically connected to the institution they were joining. Approximately half of the $2.3 billion consideration was expected to be paid in CBIZ shares, calculated at a fixed reference price of $76.84. The structure turned former Marcum partners into substantial CBIZ shareholders and made the public company’s future share price part of their personal transaction economics. (CBIZ – Definitive Proxy Statement for the Marcum Acquisition)
Only part of those shares would be delivered immediately. Most were scheduled to be distributed in monthly instalments over three years, while a smaller performance-linked portion remained subject to continued service until the fourth anniversary of closing. What appeared externally as a corporate acquisition therefore also functioned internally as a multiyear ownership transition, using listed equity to align hundreds of professionals with the future performance of the enlarged institution.
The Grant Thornton transaction arrives before that transition has fully run its course. At closing in November 2024, CBIZ agreed to issue approximately 14.3 million shares to Marcum partners, with more than 10.6 million scheduled for delivery in monthly instalments beginning in January 2025. The enlarged institution will now change ownership while the original alignment period is still underway. Marcum partners exchanged part of their ownership in a private partnership for a prolonged stake in a public consolidator; before that transition was complete, the consolidator itself agreed to disappear into a privately controlled platform. (CBIZ – Marcum Closing Disclosure)
Marcum also brought a recent history that made scale inseparable from audit quality. During the SPAC boom, the firm more than tripled its number of public-company clients and audited more than 400 SPAC initial public offerings during 2020 and 2021. The SEC concluded that the pace of expansion exposed widespread and pre-existing deficiencies in Marcum’s quality-control system, finding violations in between 25 and 50 per cent of the audits reviewed for several standards and imposing a $10 million penalty. (SEC – Marcum Quality-Control Enforcement Action)
In a parallel action, the PCAOB imposed a further $3 million penalty and required Marcum to appoint a chief quality officer and create an audit oversight committee. It was the first time a settled PCAOB order had required changes of that kind to a firm’s supervisory structure. CBIZ was therefore not simply purchasing revenue, talent and public-company audit clients. It was absorbing a firm whose rapid growth had demonstrated what happens when commercial expansion outpaces the professional infrastructure required to govern it. The Grant Thornton acquisition now transfers that responsibility again before the institutional work created by the first combination can be regarded as complete. (PCAOB – Marcum Quality-Control Sanctions and Required Supervisory Changes)
What Grant Thornton Bought
Grant Thornton is not acquiring a distressed platform in need of rescue. In the first quarter of 2026, CBIZ reported $849 million of revenue, $162 million of net income and $244 million of adjusted EBITDA, while operating cash flow and free cash flow both increased substantially from the previous year. Management described the period as the organisation’s first busy season operating as a fully integrated business and raised its adjusted earnings outlook while maintaining its revenue and free-cash-flow expectations. (CBIZ – First-Quarter 2026 Financial Results)
Those results do not establish that every part of the Marcum integration had been completed or that the enlarged institution had reached its mature economics. They do establish that the Grant Thornton transaction was not an emergency response to operational collapse. The buyer is acquiring a functioning and profitable organisation that had absorbed much of the immediate disruption created by the largest acquisition in its history.
The financial statements nevertheless reveal how much of the value remained dependent on integration assumptions. During 2025, CBIZ recorded approximately $89 million of costs related to the Marcum integration and almost $75 million of amortisation associated with acquired intangible assets. The Marcum purchase also created roughly $1.44 billion of goodwill, representing expected earnings, cross-selling opportunities, workforce expertise, efficiencies and cost savings rather than assets that could be separated easily from the people and systems producing them. Grant Thornton is therefore paying for an institution whose value depends heavily on retention, operating-model integration and the conversion of anticipated synergies into durable cash flow. The accounting value had already been recognised; the institutional value still had to be reproduced. (CBIZ – Fourth-Quarter and Full-Year 2025 Financial Results; CBIZ – 2025 Annual Report and Form 10-K)
CBIZ is also being transferred into a platform undergoing an even faster expansion of its own. Since New Mountain Capital’s investment, Grant Thornton Advisors has been combining firms across national boundaries, acquiring specialist capabilities and aligning independent audit practices with shared commercial, technological and delivery infrastructure. By May 2026, nearly twenty aligned firms representing almost 25,000 professionals had joined the multinational platform, even before the addition of CBIZ. (Grant Thornton Advisors – Expansion of the Multinational Platform)
The acquisition therefore joins two institutions that are both still being assembled. CBIZ’s scale, financing and operating model were reshaped by Marcum, while Grant Thornton’s private-capital-backed platform is expanding faster than its institutional design has yet been tested. CBIZ contributes clients, infrastructure, specialist capabilities and a significant public-company audit franchise, but also the unfinished work of integrating Marcum and a network of professional relationships whose value depends on retention and trust. Grant Thornton must preserve what CBIZ has built while deciding which systems, brands, leadership structures and practices will survive inside the larger platform. Integration cannot be reduced to placing two income statements under common ownership; it requires constructing a shared institution from organisations whose own transformations remain incomplete.
Private Ownership Replaces One Set of Constraints With Another
The move into private ownership changes the environment in which CBIZ will be governed, but it does not remove the institutional constraints surrounding the business. The company will no longer have a publicly traded share price, dispersed external shareholders or the same quarterly disclosure obligations. Decisions about investment, integration and organisational redesign can be negotiated among a smaller group of owners rather than continually interpreted through movements in the public market.
That concentration may be useful as Grant Thornton combines two large operating platforms and separates CBIZ’s Benefits and Insurance Services business at the same time. It does not make the regulated perimeter disappear. The associated audit firms must remain professionally independent, prohibited services remain prohibited and the economics surrounding attest work must still be separated from responsibility for audit judgements. Private ownership may make the architecture easier to govern, but it cannot simplify away the architecture itself.
The potential advantage lies less in a theoretically unlimited investment horizon than in the concentration of strategic control around a platform already pursuing a defined programme of expansion. Grant Thornton Advisors has used the New Mountain investment to combine national firms, add specialist businesses, expand shared delivery capabilities and commit $1 billion over three years to artificial intelligence and technology. A privately controlled platform may be able to standardise systems, reorganise service portfolios, change partner economics and absorb temporary integration costs without every decision being reflected immediately in a listed share price. (Grant Thornton and New Mountain Capital – Closing of the Growth Investment; Grant Thornton Advisors – $1 Billion Investment in Artificial Intelligence and Technology)
That freedom comes with a different financial discipline. The New Mountain transaction was financed partly through a $2.175 billion senior secured credit facility, and S&P assigned Grant Thornton a speculative-grade B rating while expecting adjusted leverage in the mid-five-times range at the end of 2024. Private ownership therefore does not replace market pressure with patient capital free of competing demands. It replaces share-price scrutiny and dispersed shareholder expectations with leverage, interest obligations, lender requirements, sponsor return targets and an eventual need to realise the investment. The relevant question is not whether private ownership is intrinsically better than public ownership, but whether its constraints are more compatible with the institution Grant Thornton is trying to build. (S&P Global Ratings – Grant Thornton Advisors Assigned a B Rating)
What Grant Thornton Must Prove
The first test is whether greater scale strengthens audit quality rather than dispersing accountability across a larger and more complicated institution. Marcum’s regulatory history makes that question impossible to treat as a matter of branding, while the PCAOB’s inspection of CBIZ CPAs confirms that the enlarged audit practice remains subject to continuing external scrutiny. Grant Thornton has been strengthening pre-issuance reviews, standardising workpapers, increasing training requirements and consolidating responsibility for assurance quality and risk under a new national leader. These measures indicate that the firm understands the challenge, but they do not resolve it. (PCAOB – Inspection Report for CBIZ CPAs; Grant Thornton – Appointment of the National Managing Partner for Assurance Quality and Risk)
The firm must integrate professionals, methodologies and quality-control systems developed under different organisations while preserving the legal independence and professional authority of the CPA firms responsible for audit opinions. The acquisition will have succeeded institutionally only if the larger platform produces more consistent supervision and professional scepticism, rather than increasing the distance between commercial leadership and the people accountable for individual audits.
The second test is whether Grant Thornton can create a genuinely shared operating platform without confusing common technology with institutional integration. The firm has launched a proprietary audit infrastructure intended to standardise data ingestion, automate workpapers and embed analytics and artificial intelligence across the audit lifecycle. The platform is being introduced first for private-company audits before a later expansion into the public-company practice, reflecting the additional controls required in the more regulated environment. CBIZ and Marcum bring their own systems, methodologies, client histories and workflows into that transition. (Grant Thornton – Launch of the GTAP Audit Transformation Platform)
Technology may reduce variation in routine execution, but it cannot by itself reconcile different risk appetites, professional cultures or approaches to judgement. The decisive moments will occur when a common process conflicts with local experience, when a migration threatens client continuity or when efficiency gains can either be extracted as financial synergies or reinvested in quality. Those choices will reveal whether integration is strengthening the institution or merely simplifying its cost base.
The final test is whether the transaction creates an institution that the next generation of professionals still wants to own, lead and remain within. Former Marcum partners entered CBIZ through a multiyear equity structure designed to keep them exposed to the future of the public company. CBIZ leaders and professionals will now enter a privately controlled platform with different economics, governance rights and liquidity expectations. Grant Thornton must demonstrate that those people are becoming participants in the institution being built rather than employees inside an increasingly financialised operating platform.
The merger agreement can transfer the listed company, cash out shareholders, determine the treatment of equity awards and establish the conditions under which Benefits and Insurance Services will be separated. It cannot transfer institutional commitment by contract. Revenue growth, cost synergies and adjusted EBITDA will show whether the acquisition works financially. Retention of respected partners, investment in professional development, audit quality, client continuity and credible ownership opportunities for future leaders will show whether it works as an institution.
Closing Thoughts
CBIZ did not become harder to keep public because its model had failed. It became harder to keep public because the model had succeeded in creating an institution far larger, more regulated and more financially complex than the one public investors had originally backed. Public capital gave CBIZ the tools to consolidate fragmented businesses, finance major acquisitions and create liquidity for successive generations of sellers. Marcum represented the high point of that strategy, but also exposed its embedded tension. The larger the audit platform became, the further independence rules reached into the surrounding commercial organisation, the more capital was required to finance growth and the more difficult it became for the public market to distinguish temporary integration costs from long-term institutional value.
The Grant Thornton transaction does not resolve those tensions. It relocates them. The listed share price disappears, ownership becomes more concentrated and management gains a clearer mandate to integrate the platform outside the daily interpretation of the public market. In return, the institution assumes greater exposure to leverage, sponsor return expectations and an eventual liquidity event. The regulated audit perimeter remains, as do the alternative-practice structure, the need to retain professionals and clients, and the obligation to convert acquired relationships into durable capability. Private ownership may provide a more suitable environment for the next phase, but only if its financial architecture leaves enough room for the patient investment that professional institutions require.
The deeper significance of the transaction lies beyond Grant Thornton and CBIZ. Professional-services firms are no longer choosing only between partnership and corporate ownership. They are combining regulated firms, commercial platforms, institutional investors, debt markets and multinational operating systems in increasingly elaborate structures. Each model solves one constraint while introducing another. Public ownership provided CBIZ with capital and liquidity, but exposed the wider organisation to market scrutiny and an expanding independence perimeter. Private ownership offers concentrated control, but introduces leverage and an exit horizon. The future of the profession will not be determined by discovering an ownership model without constraints, but by whether firms can design ownership, governance and economics around the institution they are actually trying to build.
What This Means for Boards
Boards should not treat ownership structure as a financing decision made after strategy has already been defined. In professional services, ownership determines which time horizons matter, where pressure accumulates, how investment is funded, who controls the platform and which stakeholders carry the consequences of institutional change. Public markets gave CBIZ access to capital and acquisition currency, but also subjected the company to share-price expectations and a widening independence perimeter. Private ownership concentrates control and may support faster integration, but introduces leverage, sponsor return requirements and an eventual exit. The relevant governance question is not which model appears more attractive in principle, but whether the constraints it creates are compatible with the firm’s economic architecture, regulatory obligations and strategic ambitions.
Boards also need to distinguish transaction completion from institutional integration. Legal ownership can change in a day; systems, client relationships, professional cultures, quality controls and partner loyalties cannot. The combination of Grant Thornton and CBIZ joins two organisations that are both still evolving, while the separation of Benefits and Insurance Services adds another layer of complexity. Boards should demand visibility into which operating model is being built, which capabilities are being standardised, where local autonomy will remain and how decisions will be made when commercial efficiency conflicts with professional judgement. Without that clarity, integration risks becoming a collection of technology migrations, cost targets and reporting lines rather than the deliberate construction of a stronger institution.
Finally, boards should measure success beyond revenue growth, adjusted EBITDA and acquisition synergies. Those metrics will show whether the transaction creates financial value for its owners, but not whether the institution is becoming more trusted, capable or resilient. Boards should track audit quality, partner and senior-professional retention, client continuity, investment in judgement and development, ownership opportunities for future leaders and the organisation’s ability to protect long-term institutional value even when doing so reduces short-term returns. In professional services, the most valuable assets are not fully owned by the firm. They remain embedded in people, relationships, reputation and professional authority. Governance must therefore focus not only on what the transaction acquires, but on whether the institution remains capable of reproducing those assets after ownership changes.
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Sources
Primary Sources
- CBIZ – Corporate History and Frequently Asked Questions
- CBIZ – 2024 Annual Report and Form 10-K
- CBIZ – 2025 Annual Report and Form 10-K
- CBIZ – First-Quarter 2025 Form 10-Q
- CBIZ – First-Quarter 2026 Form 10-Q
- CBIZ – Third-Quarter 2024 Form 10-Q
- CBIZ – Marcum Acquisition Form 8-K and Transaction Materials
- CBIZ – Definitive Proxy Statement for the Marcum Acquisition
- CBIZ – Fourth-Quarter and Full-Year 2025 Financial Results
- CBIZ – First-Quarter 2026 Financial Results
- Grant Thornton and New Mountain Capital – Closing of the Growth Investment
- Grant Thornton Advisors – $1 Billion Investment in Artificial Intelligence and Technology
- Grant Thornton Advisors – Expansion of the Multinational Platform
- Grant Thornton – Appointment of the National Managing Partner for Assurance Quality and Risk
- Grant Thornton – Launch of the GTAP Audit Transformation Platform
- SEC – Marcum Quality-Control Enforcement Action
- PCAOB – Marcum Quality-Control Sanctions and Required Supervisory Changes
- PCAOB – Inspection Report for CBIZ CPAs