Your startup has outgrown spreadsheets and month-end guesswork.
Investors are asking harder questions.
The board wants a forecast it can trust.
And someone on the team says: “We need a CFO.”
In short: a fractional CFO is a senior finance leader who works with your company part-time, while a full-time CFO is an executive employee dedicated entirely to your business. For most early-stage and many growth-stage startups, a fractional CFO delivers the strategic expertise they need at a fraction of the commitment. A full-time CFO makes sense when finance complexity, deal flow and leadership demands fill a full week, every week.
In this guide, we’ll explain what each model involves, how they compare, and which signals point to one or the other.
What is a fractional CFO?
A fractional CFO (sometimes called an outsourced, part-time or on-demand CFO) is an experienced chief financial officer who serves several companies, each for a defined share of their time.
This isn’t a bookkeeper with a bigger title. A good fractional CFO works on the same strategic questions a full-time CFO would:
- Financial strategy and planning: budgets, forecasts and scenario models.
- Fundraising support: investor materials, financial models, due diligence and term discussions.
- Board and investor reporting: clear monthly or quarterly packs with the KPIs that matter.
- Cash and runway management: tracking burn and flagging problems early.
- Building the finance function: choosing systems, setting controls and deciding when to hire.
The difference is in how much time they spend, not in the level of thinking they bring. Our guide to strategic CFO services on demand covers the model in more detail.
What does a full-time CFO do differently?
A full-time CFO is a member of the executive team, employed by the company and focused on it alone.
Beyond the strategic work above, a full-time CFO usually:
- Leads a finance team day to day, including controllers, accountants and FP&A analysts.
- Owns relationships with investors, banks, auditors and key partners on an ongoing basis.
- Is available at any moment for negotiations, pricing decisions or operational issues.
- Handles constant transactions: frequent fundraising, M&A, debt facilities or preparation for an IPO.
That presence is valuable, but only when the company has enough complexity to use it.
Fractional CFO vs full-time CFO: how do they compare?
The table compares the two models on the factors founders ask about most. Actual costs and scope always vary by company, provider and stage:
| Factor | Fractional CFO | Full-time CFO |
|---|---|---|
| Cost structure | Monthly retainer or project fee, scaled to the hours and scope you need | Full executive salary, plus benefits, equity and recruiting costs |
| Commitment | Flexible, can be scaled up or down as needs change | Long-term employment, harder and slower to change |
| Time to start | Usually quick, since there’s no long executive search | Recruiting a senior executive can take months |
| Scope | Strategic finance, fundraising, reporting and planning, often alongside an outsourced finance team | Full ownership of finance, team leadership and daily executive involvement |
| Availability | Defined hours, with support around key events | Available full-time, every day |
| Breadth of experience | Sees many companies, stages and situations | Deep knowledge of one company |
| Equity | Usually little or none | Typically expects a meaningful equity grant |
| Best stage | Pre-seed to growth stage, or companies between CFOs | Later-stage companies with high complexity, large teams or frequent transactions |
When is a fractional CFO the right choice?
A fractional CFO is usually the better fit when your company needs senior financial judgment, but not 40 hours a week of it.
Common signals:
- You’re preparing to raise. You need a credible model, a clean data room and someone who can answer investor questions, but the intense work comes in waves.
- Your board wants better reporting. Monthly packs, KPIs and variance analysis need structure, not a full-time executive.
- Cash is tight. Every hire affects runway, and you want to spend on product and growth first.
- You’ve outgrown your bookkeeper. The books are accurate, but nobody is turning them into decisions.
- You’re expanding into a new market. For example, setting up an Israeli subsidiary or US operations, where you need guidance on structure and processes without a permanent local hire.
- You’re between CFOs. A fractional CFO can bridge the gap and help define the profile for the next full-time hire.
A fractional CFO also works well alongside an outsourced finance team handling bookkeeping, payroll and compliance. Our article on when to outsource and when to keep functions in-house explains how to split the work.
When do you need a full-time CFO?
The answer changes when finance work fills the week and the CFO’s absence starts to slow the company down.
Signals that it may be time:
- Transactions are constant. You’re raising larger rounds, negotiating debt, evaluating acquisitions or preparing for an IPO.
- The finance team is growing. Several people need daily leadership, review and development.
- Operations are complex. Multiple entities, currencies, revenue streams or regulated activities create daily decisions.
- Investors expect it. At later stages, some investors and boards want a dedicated CFO on the executive team.
- Strategic decisions can’t wait. Pricing, hiring plans and spending trade-offs need a finance voice in the room every day.
Even then, many companies move gradually: a fractional CFO increases their hours first, and the full-time hire follows when the need is proven.
Is a fractional CFO the same as a financial controller?
No, and confusing the two is a common mistake.
A financial controller focuses on accuracy and control: closing the books, reconciliations, internal controls and reporting on what has happened. A CFO, fractional or full-time, looks forward: planning, fundraising, strategy and helping the CEO decide what should happen next.
Many startups need both, at different intensities. A typical setup is an outsourced controller and bookkeeping team, with a fractional CFO overseeing strategy. Our guides to financial controller vs CFO and when to hire a controller, FP&A or CFO go deeper.
What does the decision look like in practice?
Illustrative example only. The company and details below are hypothetical and are meant to show the decision process, not typical costs or outcomes.
A SaaS startup with a US parent company and an R&D subsidiary in Israel has just closed its Seed round. The CEO handles finance with an external bookkeeper, and the board has asked for a proper forecast and monthly reporting.
The founders consider hiring a full-time CFO. Before deciding, they map the actual work:
- A 13-week cash forecast and an annual budget, updated monthly.
- A monthly board pack with burn, runway and core SaaS metrics.
- Intercompany setup between the US and Israeli entities.
- Series A preparation, which they expect to start in about a year.
When they list it out, the strategic work fills a few days a month, with peaks around board meetings and fundraising. They choose a fractional CFO, supported by an outsourced bookkeeping and payroll team.
Twelve months later, as the Series A process begins, the fractional CFO increases their involvement to lead the model and due diligence. After the round, with a growing team and two more entities planned, the company starts recruiting a full-time CFO, and the fractional CFO helps write the job profile and hand over.
How do you decide? A step-by-step approach
- List the finance work you need in the next 12–18 months: reporting, forecasting, fundraising, systems, team and compliance.
- Separate strategic from operational work. Bookkeeping and payroll don’t require a CFO. Planning and investor work do.
- Estimate the time the strategic work really takes, including peaks around fundraising and board meetings.
- Check your runway. Use your cash forecast to see what each option does to burn. Our guide to burn rate and runway can help.
- Consider what investors and the board expect at your current and next stage.
- Plan the transition. Decide in advance which milestones would trigger a move from fractional to full-time.
A practical fractional vs full-time CFO checklist
- ☐ We’ve listed the finance work needed over the next 12–18 months
- ☐ We’ve separated strategic CFO work from bookkeeping and payroll
- ☐ We know roughly how many hours of strategic work we need each month
- ☐ We’ve modeled the impact of each option on burn and runway
- ☐ We know what our board and investors expect from finance reporting
- ☐ We have a fundraising timeline and know who will lead the finance side
- ☐ We’ve considered multi-entity needs, such as a US parent and an Israeli subsidiary
- ☐ We’ve defined the milestones that would justify a full-time CFO
- ☐ We have a plan for handover if we move from fractional to full-time
How Brooks Keret can help
At Brooks Keret, our CFO team works with startups and growing companies as fractional CFOs, providing strategic finance leadership without the commitment of a full-time executive hire.
We help founders build forecasts and budgets, prepare for fundraising, set up board reporting and manage cash. Because we also provide bookkeeping, payroll and compliance services in Israel and the US, we can support the whole finance function, and help you plan the move to a full-time CFO when the time comes. Learn more about our CFO services.
Frequently asked questions
What is the main difference between a fractional CFO and a full-time CFO?
A fractional CFO works with your company part-time, usually on a retainer, while a full-time CFO is an executive employee dedicated only to your company. Both can provide strategic finance leadership. The difference is time commitment, cost structure and day-to-day involvement.
Is a fractional CFO cheaper than a full-time CFO?
In most cases, yes, because you pay only for the time and scope you need, without a full executive salary, benefits or a large equity grant. The actual cost varies by provider, scope and company complexity.
When should a startup hire a fractional CFO?
Common triggers include preparing for a fundraising round, needing better board reporting, outgrowing a bookkeeper, managing a tight runway or expanding into a new market. If you need senior financial judgment but not full-time, a fractional CFO is often a good fit.
When should a company switch to a full-time CFO?
Usually when finance work fills a full week on an ongoing basis: frequent transactions, a growing finance team, complex multi-entity operations, or investor expectations for a dedicated CFO on the executive team.
Can a fractional CFO help with fundraising?
Yes. Fundraising support is one of the most common reasons companies engage a fractional CFO, including building the financial model, preparing the data room, supporting due diligence and reviewing terms.
Can a fractional CFO work with an Israeli subsidiary?
Yes. A fractional CFO with cross-border experience can help structure finance operations between a parent company and an Israeli subsidiary, coordinate local bookkeeping and payroll, and keep reporting consistent across entities.
The bottom line
The choice between a fractional and a full-time CFO isn’t about how important finance is. It’s about how much senior finance time your company actually needs right now.
For most startups, a fractional CFO provides the strategic leadership they need, with flexibility and without straining runway.
A full-time CFO becomes the right move when complexity, transactions and team size fill the week.
Map the work. Check the numbers. Decide on the milestones that will trigger the next step. And make sure, at every stage, that someone experienced is looking ahead, not just keeping the books.
