The Human Side of M&As

Why EIN Integration Is a Critical Step in M&A Workforce Transitions 

An EIN is more than just a tax ID — it’s the legal identity of an employer. Every aspect of an employee’s work relationship flows from it: paychecks, W-2s, taxes, and benefits eligibility. That’s why, in M&As, the EIN transition is one of the most critical parts of workforce integration, and it’s often central to the success of a newly acquired organization’s transition.   

For employees, the shift isn’t always obvious. An organization might change its name overnight, new signage might go up, and leadership may start referring to a new parent organization. But until employees are formally moved under the acquiring company’s EIN, their pay stubs, tax records, and benefits remain tied to the old entity. In effect, they’re still legally employed by their prior organization. That was the case when USC acquired Methodist Hospital of Southern California. Even after the name changed to USC Arcadia, staff remained on Methodist’s EIN until the full transition took place.  

Executing this move required a massive effort behind the scenes. Methodist employees had to be migrated into USC’s HRIS and payroll systems, their employment records had to be reissued under USC’s EIN, and their benefits needed to be restructured. During the transition, USC opted for a hybrid approach — preserving some of Arcadia’s lower-cost, high-quality benefits while aligning others with USC’s programs. At the same time, legacy payroll processes and some benefit vendor integrations were retired and replaced with USC’s systems.   

It’s important to note that EIN integration is not just a paperwork exercise. It’s a significant step in going from partial integration to full integration in transitioning the employee status of USC Acadia as part of USC — legally, financially, and operationally.  

Setting the Stage: Listening and Assessment   

The EIN transition for USC Arcadia began with deliberate listening and alignment. Before strategy or implementation could take shape, it was essential to understand the transition efforts already underway and build cohesion among HR leaders at both the system and local levels. Establishing synergy, governance structures, and defined workgroups was important to ensure that planning was thorough and intentional before any design work began. 

By March 2023, after an eight-month assessment, the first master planning workshop was convened, followed by additional sessions to clarify timing, scope, and methodology. These strategy sessions, involving leaders from USC, Keck Medicine, USC Arcadia, and consulting partner Chartis, laid the foundation for a unified road map. By early 2024, the “when, what, and how” of the integration was in place, with Jan. 1, 2025, set as the official date for all Methodist Hospital employees to formally transition under USC’s EIN.  

How Governance and Project Management Eased the Transition  

The USC Arcadia transition was guided by a 15-month integration road map developed through collaboration between Keck Medicine’s HR team, university partners, and finance and IT departments. The scope was extensive, requiring cross-disciplinary coordination with more than 100 contributors working across 11 designated work lanes, including system integrations, communications, employee leave, learning management, benefits, compensation, job architecture, payroll, and tax.  

Merging a hospital into a larger health system brought both operational and financial considerations. Beyond the technical and compliance demands, we had to evaluate the benefits cost structure of the acquired entity. The challenge was to balance efficiency and accessibility against the need for alignment with USC’s broader benefits framework. In some cases, maintaining lower-cost, high-quality offerings was preferable to enforcing a centralized model that could overlook entity-specific needs. 

To manage such complexity, strong governance and disciplined project management were essential. Governance structures clarified accountability, ensuring the right stakeholders reviewed and approved changes to budget, scope, and timelines. They also resolved escalated issues, provided updates to the board, and reinforced transparency. These mechanisms enabled full alignment across functions, timely decision-making, and confidence that the integration outcomes were delivered with both rigor and clarity.   

Effective the first pay period of 2025, all Methodist Hospital employees became USC employees, establishing the success of an initiative that involved more than 100 project participants, 99 new or remediated integrations, and 1,500 employees plus 300 contractors being migrated from API to Workday.  

While the cultural integration process remains ongoing, this collaborative effort generated several insights that can guide HR executives in leading similar initiatives.  

5 Key CHRO Competencies and Guidance  

Successful integrations demand both operational precision and cultural leadership. HR leaders can navigate this complex process by focusing on five essential competencies that drive lasting impact:  

1. Prioritize Cultural Aspects Throughout the Integration Process 

Cultural assimilation isn’t just a step of the M&A process — it’s the foundation. And while assimilation doesn’t happen overnight, culture must be the starting point of any successful integration strategy. That foundation is best laid when the approach to process and system integrations is being discussed.   

Culture is intangible and carries significant personal value for members of an organization. In health care, it affects the quality of care and patient outcomes. Deeply embedded cultural norms can pose a significant risk to the success of an integration effort in M&A situations. Therefore, recognizing cultural nuances throughout the integration process is important, especially for workforce integration efforts. 

2. Assess the Existing Systems Before Making Any Changes 

Transitioning to a new EIN is a complex process that requires careful planning and thorough understanding of the existing setup of the acquired entity. Employee management systems, including total rewards packages, recruitment and retention strategies, performance management methods, and employee development processes, operate as integrated frameworks in which modifying one component impacts the others.  

It is imperative to understand that policies inform practices and become formalized over time. Although policy changes can be quickly implemented in writing, altering the practices linked to former policies requires substantial effort and effective change management strategies. It’s important to ensure systematization won’t hinder daily operations of management.  

3. Clearly Define Responsibilities for All Contributors  

The success of a transition process hinges on clearly defining the roles of all contributors, whose collaboration — whether significant or minor — will determine the outcome of your initiative. In our case, the success of integrating Arcadia’s workforce relied on involving the university HR team as essential contributors, because the EIN transition of USC Arcadia included HR technology, benefits, and payroll, all managed centrally within a shared services model by the university, the parent organization of Keck Medicine of USC.  

Such large projects require early alignment and commitment from all stakeholders. Even if a solid governance structure is implemented, its effectiveness is largely dependent on the clear establishment of collaboration and accountability from the outset.   

4. Energize Cultural Transformation 

The full value of a merger can only be realized if an effort is made to build and leverage organizational synergies beyond the transactional aspects of logistical operations. The culture integration process should include:   

• Cultural alignment. Accelerate change and elevate every moment of the employee experience through listening efforts with employees at all levels, across all facilities.  

• Value proposition repositioning. This included the development of a new system narrative to attract, retain, and foster meaningful connections with both consumers and patients, as well as top talent in a highly competitive market.  

• Redefinition of (and re-emphasis on) the value of every employee. Ensure that every employee knows how they contribute to who you are, how you operate, and where you are going.  

The integration process takes place over time. Focusing on cultural assimilation is critical and essential to successfully integrate new employees and foster a positive workplace culture.   

Our cultural integration process continues through the gradual launch of our key system programs at USC Arcadia along with embracing the good in the hospital’s existing operations and extending those to the system level where possible. This approach has helped us build credibility with local leadership and convey sincerity in our welcoming approach.   

5. Stay Engaged and Aware — Without Micromanaging 

The saying, “It takes a village,” exemplifies the success of large-scale M&A initiatives. The CHRO’s role can be challenging, as it demands walking the fine line between control and empowerment, between specific direction and organic evolution, and above all maintaining a balance between the financial realities and employer obligations of a system structure. While leading the multiple stakeholder relationships is a critical responsibility of the CHRO, the need to secure alignment and agreement for financially sensitive decisions with system and entity CEOs and CFOs is a must.  

Honoring the network of relationships in a matrix environment and the values that bind different entities together can go a long way in carving out a winning strategy and execution for such integration initiatives. Leaders who are undertaking similar journeys should ensure that: 

• Organizational leaders are engaged, committed, and supportive of the process.  

• Decisions are made at the right level, in a timely and definitive manner. 

• Decisions and outcomes are understood across the project and associated teams.  

• Teams attend and actively participate in scheduled meetings to support ongoing communication and transparency. 

• Key milestones and wins are recognized and celebrated.  

The Assimilation Continues 

At Keck Medicine of USC, we ensured that leaders at various levels of the organization helped guide the reidentification and assimilation processes to successfully integrate a large hospital with thousands of employees into our unified health system.  

The road map to a successful integration isn’t simply logistical. A merger is a multifaceted coalition of cultural and operational elements. A large cornerstone in making our merger successful was helping employees adapt and feel a new sense of belonging and workplace identity as a Keck Medicine of USC employee.  

The logistical and legal processes to merge the hospital with our health system demanded paying attention to detail, key timelining, and developing a helpful partnership with an outside consultant. Additionally, creating the culture transformation has been essential in building a cohesive environment of an employee’s feeling of belonging to a new organization.      

Ekta Vyas, Ph.D., is the CHRO for Keck Medicine of USC, the academic medical system of the University of Southern California, and an adjunct professor at USC Marshall School of Business.