What Open Book Partners does

Open Book Partners (DBA: OB Partners) is a New York-based, founder-led outsourced CFO consulting firm established in 2022 by Harry O'Sullivan (CFA, CPA). The firm delivers fractional CFO services, financial modeling and forecasting, fundraising and capital strategy support, investor relations and due diligence preparation, scenario planning and risk analysis, and board/stakeholder reporting to startups and growth-stage companies, with an expanded segment covering M&A and exit transactions. The firm operates with a small team of 1-10 employees and delivers its services as professional consulting engagements rather than software products, integrating into client teams as an extension of the financial function.

The service offering is structured as recurring/subscription engagements initiated through consultation bookings. No pricing tiers or rates are publicly disclosed. The go-to-market is sales-led and direct, with prospective clients booking consultations via Calendly linked to the founder's calendar. Distribution is domestic, concentrated in New York, USA. Marketing relies on content marketing (blog articles on topics such as tax planning, equity dilution, and unit economics), a founder-led LinkedIn presence, and an email newsletter — all top-of-funnel channels designed to drive consultation bookings rather than self-service acquisition.

The firm's brand is anchored in the founder's personal track record: over a decade of experience investing tens of millions across fintech, AI, and proptech, more than $70M personally raised for startups, and $100M+ in client venture capital and debt facilitated under the firm's engagement. Reported client outcomes include 5x average revenue growth. Open Book Partners has raised no disclosed external funding, holds no patents, and reports no partnerships or alliances; the operating model is a boutique consulting practice whose core asset is the founder's relationships and execution reputation.

Name

Open Book Partners

Legal name

Open Book Partners

Website

https://openbookpartners.com

Company type

Private

Founded year

2022

Operating status

Operating

Headcount range

1–10 employees

Short description

Open Book Partners (OB Partners) is a New York-based outsourced CFO consulting firm founded in 2022 by Harry O'Sullivan (CFA, CPA), delivering fractional CFO, financial modeling, fundraising, and investor relations services to startups, growth-stage companies, and M&A/exit-adjacent businesses.

Ownership category

akta.pro rank

Product category

Outsourced Financial Consulting

NAICS

Other Management Consulting Services (541618), Management Consulting Services (54161)

SIC

Services-Management Consulting Services (8742), Investment Advice (6282)

akta.pro primary industry

Outsourced Finance & CFO Services (BPAHABAE)

akta.pro secondary industry

Corporate Finance & Capital Advisory (BPAHADAB)

Keywords

• Fractional CFO services
• Outsourced financial leadership
• Fundraising advisory
• Financial modeling consulting
• Investor relations support

Headquarters

HQ city

New York

HQ country

United States

HQ region

North America

Offices1 record

Markets served

GTM type

B2B

Offering type

Services

Cost components

Personnel, Operations, Marketing or Sales, Technology or R&D

Revenue model

1. Outsourced CFO / Fractional CFO Services: Ongoing consulting engagement providing financial leadership, strategic guidance, and executive-level CFO support to startups and growth-stage companies without the cost of a full-time CFO.

Go-to-market motion1 record

Distribution channels1 record

Marketing channels4 records

Core offering

Open Book Partners provides outsourced CFO consulting for startups and growth-stage companies, including fractional CFO leadership, financial modeling and forecasting, fundraising and capital strategy, investor relations and due diligence preparation, scenario planning and risk analysis, board and stakeholder reporting, and ancillary services such as FP&A, KPI tracking, and M&A advisory. Engagements are scoped on a consultation basis and delivered by the founder and team.

Product overview

Open Book Partners is an outsourced CFO consulting firm that provides a comprehensive suite of financial advisory services for startups and growth-stage companies. The offering is organized as a unified consulting service with core capabilities (Fractional CFO Services, Financial Modeling & Forecasting, Fundraising & Capital Strategy, Investor Relations & Due Diligence, Scenario Planning & Risk Analysis, and Board & Stakeholder Reporting) supplemented by specialized add-on services (Annual Budgeting & Cash Flow Management, Financial Planning & Analysis, M&A Support, and KPI Development & Performance Tracking). These services are delivered as professional consulting engagements rather than software products, with the firm acting as an extension of the client's financial team.

Differentiator

Problem solved

Functional benefit

Products and services

• Fractional CFO Services Part-time executive financial leadership integrating into client teams to deliver strategic guidance, financial oversight, and tailored financial solutions for startups and growth-stage companies.
• Financial Modeling & Forecasting Building data-driven financial models that provide visibility into revenue projections, expenses, and cash flow to support informed business decisions for founders and finance leaders.
• Fundraising & Capital Strategy Supporting businesses in raising debt or equity capital, including developing financial narratives, preparing investor-ready reports, and navigating term sheets to secure funding.
• Investor Relations & Due Diligence Managing investor relationships, preparing comprehensive data rooms and due diligence materials, and ensuring startups present financials in a way that inspires investor confidence.
• Scenario Planning & Risk Analysis Developing contingency strategies and modeling different financial scenarios to help businesses prepare for market shifts, downturns, and expansion opportunities.
• Board & Stakeholder Reporting Creating comprehensive financial reports and dashboards tailored for boards, investors, and leadership teams to keep stakeholders aligned and informed.
• Annual Budgeting & Cash Flow Management Helping businesses build structured annual budgets, optimize spending, and create cash flow strategies that ensure financial resilience throughout the year.
• Financial Planning & Analysis (FP&A) Transforming complex financial data into actionable strategies through forward-looking analysis of revenue trends, profitability, and key performance indicators.
• Mergers & Acquisitions (M&A) Support Guiding businesses through financial due diligence, valuation assessments, and deal structuring to maximize transaction value while minimizing risk.
• KPI Development & Performance Tracking Identifying, defining, and monitoring key performance indicators aligned with strategic goals, providing real-time insights into financial health and operational efficiency.

Quantifiable outcome

• 5x average revenue growth for client companies
• +2 more outcomes

Named customers3 records

Segments3 records

Ideal customer profiles2 records

Technology focussed No

API detail

Has API

No

API docs

API detail

Core technology

AI maturity

App detail

Scale indicators5 records

Recent moves4 records

Expansion highlights4 records

Broad incumbents

• RSM US: Large accounting and consulting firm providing CFO advisory, transaction services, and FP&A support to mid-market and growth-stage clients. Comparable in delivering outsourced CFO work but as part of a much wider service portfolio.
• BDO USA: Major accounting and advisory firm offering outsourced CFO, financial modeling, and transaction advisory services. Overlaps with OB Partners' service menu but operates at much greater scale and breadth, serving both startups and larger enterprises.
• PwC (Private Company Services): Big Four firm offering CFO advisory, transaction support, and investor relations services. Provides overlapping capabilities with OB Partners but targets a much broader client base and benefits from scale and brand recognition.
• Withum: Mid-market accounting and advisory firm with a dedicated venture capital and emerging-company practice offering CFO advisory, audit, and tax services. Provides overlapping startup-focused CFO capabilities but as part of a full-service firm.

Direct peers

• CFO Suite: Outsourced and fractional CFO services provider for early- and growth-stage companies. Comparable in delivering fractional CFO engagements, financial modeling, and fundraising support to venture-backed clients.
• Acuity CFO: Fractional CFO firm providing financial leadership, fundraising support, and FP&A to high-growth and venture-backed startups. Directly overlaps with OB Partners' core service offering and target customer.
• Pilot: Tech-enabled bookkeeping, tax, and CFO services firm focused on startups and small businesses. Closely comparable in customer segment (startups), CFO-tier service offering, and subscription recurring revenue model.
• VCFO: Provider of fractional and interim CFO services to growth-stage and venture-backed companies. Comparable in delivering senior financial leadership, financial modeling, and capital strategy on a subscription/engagement basis.
• Kruze Consulting: A leading outsourced CFO, accounting, and tax firm specifically serving venture-backed startups. Directly comparable in target customer (VC-backed startups), service mix (fractional CFO, financial modeling, fundraising support), and founder-led service model.

Emerging players

• Versa Business Advisors: Emerging fractional CFO and financial advisory boutique focused on startups and SMBs. Comparable in targeting similar customer segments and offering part-time CFO support, though typically with a smaller client base than OB Partners.

Market position

Strengths4 records

Weaknesses4 records

Competitive moat3 records

Key risks5 records

Key highlights5 records

Customer concentration

• LinkedInlinkedin.com/company/ob-partners

Revenue estimate

Valuation estimate

Number of profiles

Profiles1 record

Funding overview

Funding rounds

Investors

Funding detail is available on the Subscription and Enterprise plan.Contact sales →

M&A

Investments

M&A and investment is available on the Subscription and Enterprise plan.Contact sales →

Frequently asked questions about Open Book Partners