At corporate credit card issuer Brex, the evolving partnership between CFO Ben Gammell and Chief Accounting Officer Erik Zhou reflects the company’s growth trajectory and is helping develop the pathway to a future IPO. As financial operations scale, so does the complexity of preparing for public markets, managing compliance and maintaining investor-ready reporting standards.
The CFO-CAO dynamic has become a critical element of Brex’s strategy, with clearly defined roles that allow for both specialization and collaboration. While Gammell focuses on long-term financial strategy and investor communication, Zhou takes ownership of the company’s accounting infrastructure, internal controls and audit readiness. With experience ranging from Gammell’s time as an investment banker at Goldman Sachs to Zhou’s background in audit at PwC, the two are building a finance organization designed to withstand scrutiny and support scalable growth.
Building a goal-oriented partnership
The partnership between Gammell and Zhou is grounded in the technical demands of building a finance function for a company aiming to go public. Rather than blur responsibilities, the two have drawn sharp lines around ownership. Where there may be areas of overlap, both say they’ve built connections where strategy and compliance must meet.
“There are some things that are 100% in my lane,” Zhou said. He noted things like “accounting policies, the audit, financial reporting and controls” are under his ownership. This not only takes some of the pressure off of Gammell but also allows the accounting team to have more of a strategic impact on the company’s long-term goals.
“I think the accounting team is at the core of IPO readiness. There’s no IPO if your financial statements aren’t bulletproof,” he added. “We’ve been building a public-company-ready foundation for years — clean audit opinions, no material weaknesses, strong documentation, automated controls and high-integrity data flows.”
That emphasis on controls is reflected in how Zhou approaches his decision-making role across the organization. “Controls also come down to how decisions get made, how data flows through our systems, how we collaborate with other departments — like RevOps, FP&A, product, legal, tax,” he said. “It’s about building confidence in our numbers and confidence in the underlying processes. A good control environment allows us to move quickly because we trust the data and we know where the risks are.”
From the CFO spot, Gammell relies on the integrity of Zhou’s systems to support decision-making at the executive and board levels. “You run the risk of garbage in, garbage out,” Gammell said when asked about data quality’s importance in decision-making and the accounting team’s role in its development. “Finance people can help drive insights and transform financial information, but they don’t necessarily produce the financials — especially on a historical basis — that accounting functions are integral for.”
Their collaboration becomes even more critical as Brex moves toward GAAP convergence. “Brex has aspirations of being a public company one day,” Gammell said. “That’s the point where you start to see much greater convergence in how financial information is reported because you start to conform to GAAP.” While many startups may rely on non-GAAP metrics to better reflect business reality, he noted, public investors “want to be able to think about your business in context — compare you across an industry set or peer set.”
Zhou, with his audit background, plays a hefty role in this process as he leads on SOX readiness and external assurance. “SOX is important and we’re building toward that,” he said. “We’re already operating at a level where we expect a significant amount of scrutiny.”
To the accounting team, that means robust internal documentation and actionable, system-based controls, Zhou explained. “It’s not just about having accurate numbers but also being able to explain those numbers to the board, to investors, and eventually to Wall Street,” he said. “That’s where finance and accounting need to be aligned.”
In areas where Gammell and Zhou may approach accounting decisions differently, they work together to assess both the audit defensibility and investor perception of each option. “Even if it’s within the range of GAAP, there’s still a range of approaches you can take to a given financial metric,” Gammell said. “And the question becomes not just, ‘How defensible is this from an audit perspective?’ but also, ‘How will investors perceive this? What would their understanding of the metric be?’” The result is a thoughtful, collaborative process — one that ensures financials are both technically sound and aligned with the company’s broader narrative.
Developing the tech stack
To support growth and prepare for public-company demands, Gammell and Zhou have worked together to build a finance tech stack that strengthens controls, speeds up reporting and improves data integrity across teams.
Zhou’s team implemented a tool to streamline the month-end close and help accounting become more proactive in identifying changes. “We use it to manage our flux analysis,” he said. “Instead of just asking, ‘Why did this expense go up?’ we can quickly tie it to an invoice, a PO or even a vendor contract.” That added layer of context allows accounting to explain variances with greater confidence and reduces reliance on manual lookups across disconnected systems.
For Gammel, the value is in getting fast, reliable answers when leadership needs them. “It integrates our accounting data, procurement data and finance data,” he said. “It saves so much time for accounting and gives finance the clarity it needs when doing the monthly flash.”
On the planning side, Brex replaced spreadsheets with a system that consolidates key data sources and provides a clearer audit trail. “It helps us have a more stable and automated financial reporting output,” Gammell said. “At this point, it’s almost entirely automated. We input the data, and it generates what we need for the monthly flash or a leadership email.”
Rather than chasing data across tools or waiting on ad hoc requests, both leaders now rely on systems that make financial data more transparent, traceable and actionable. “If something changes, we know why it changed and who changed it,” Gammell said.
Synchronizing talent development
As Brex has scaled, both Gammell and Zhou explained how they’ve placed a premium on building a finance and accounting team that not only performs at a high level but sticks around long enough to grow with the business. At a company preparing for the long road to IPO, institutional knowledge and operational continuity are treated as strategic assets.
Zhou, who has grown the accounting team from two people to more than 30, said the first thing he looks for is passion for the craft. “That may sound basic, but it’s important — people who genuinely care about getting things right, about understanding the why behind the rules and about the impact of what they’re doing on the business,” he said. Adaptability is also key: “At a company like Brex, things change fast. You need people who are excited about that, not just tolerant of it.”
“It’s perfectly fine for a finance team to spike into the red zone in terms of capacity every now and then, but you don’t want to live there.”
Ben Gammell
CFO, Brex
He’s also invested in giving team members stretch opportunities across functions, which has helped develop business fluency outside of traditional accounting roles. “We’ve had folks on the accounting team move into finance, systems, and even product,” Zhou said. “That’s a big win. If we can develop people who are not only great accountants but also understand the broader business, we all benefit.”
Gammell emphasized the importance of hiring people who take pride in their work and aren’t just chasing the next milestone. “If you hire folks whose motivation is a medium- or long-term event, like an IPO or fundraise, those events are few and far between,” he said. “They’re not sustaining motivation day to day.” Instead, he said he looks for people with curiosity and craftsmanship. “People who are always looking to make things more efficient, or go deeper in their understanding, or unlock a new insight — that’s who we look for,” Gammell said.
That mindset, both say, helps reduce burnout and attrition — two major risks in a fast-paced environment. “It’s perfectly fine for a finance team to spike into the red zone in terms of capacity now and then, but you don’t want to live there,” Gammell said. Giving people space to recover after sprints, he added, is part of what helps strong team members stay invested for the long haul.
