Your CFO Partner for Growth
At Open Book Partners, we do more than just manage numbers—we unlock the financial potential of your business. With a deep understanding of financial strategy and capital markets, we help companies raise capital, build strong financial foundations, and navigate complex business landscapes with confidence.
What Sets Us Apart
Data-Driven Decision Making
Investor-Ready Financial Models
Scalable Growth Strategies
Access to Investor Networks
Proven Track Record
Meet the Visionary Behind OB Partners
Harry O'Sullivan, CFA, CPA, has spent over a decade helping startups and high-growth companies scale successfully. With experience investing tens of millions across fintech, AI, and proptech, and securing over $70M in funding for startups, Harry understands what it takes to build financial strategies that drive growth. As a trusted CFO partner, he empowers businesses with the financial clarity needed to thrive in a competitive market.
Explore Our Solutions
Financial clarity is the foundation of every successful business. Whether you need support with fundraising, financial modeling, or strategic planning, our outsourced CFO services empower you to scale with confidence.
Fractional CFO Services
Expert financial leadership without the full-time cost, providing strategic guidance for growth.
Financial Modeling & Forecasting
Building data-driven financial models to help you make informed, future-proof business decisions.
Fundraising & Capital Strategy
Supporting businesses in raising debt or equity capital, ensuring a strong financial foundation.
Investor Relations & Due Diligence
Helping you navigate investor conversations and financial transparency with confidence.
Scenario Planning & Risk Analysis
Developing contingency strategies to navigate financial uncertainties and market shifts.
The Perfect Customer Experience
"Harry’s transparency and insight in portfolio reporting are invaluable. His comprehensive data rooms provide new investors with the clarity needed for informed decisions, especially during later-stage fundraising."
TX Zhou
General Partner, Fika Ventures
"Harry brought invaluable expertise to Bowery’s finance function, from scenario planning to system implementation and investor relations. His work kept both our management team and investors informed and confident."
Noah Isaacs
CEO, Bowery Valuation
"Harry’s expertise in analyzing complex data was invaluable, from uncovering true unit economics to evaluating investment opportunities. His insights played a key role in guiding a portfolio company through a successful Series B raise."
Adam Plotkin
VC Investor, Board Member