- Fractional CFOs work part-time on an ongoing retainer — typically 2–4 days per month — and are best for companies that need consistent strategic finance leadership without a full-time hire.
- Interim CFOs are full-time, temporary replacements — deployed for 3–12 months to cover a departure, run a transaction, or stabilise finance before a permanent hire.
- The trigger for interim is usually an event: a CFO resignation, an imminent fundraise, a sale process, or a financial crisis. Fractional is a steady-state operating choice.
- Cost is meaningfully different: interim CFOs commonly run $1,500–$2,500/day or $25,000–$40,000/month; fractional retainers average $5,000–$10,000/month.
- Neither is inherently better — the right answer depends entirely on whether your need is ongoing or episodic.
Founders use "fractional" and "interim" interchangeably. They mean different things, and picking the wrong model costs time and money. Here is a clean decision framework for choosing between them.
What fractional means
A fractional CFO works with your company part-time on a recurring basis — usually 2–4 days per month, sometimes more at peak periods. The engagement runs on a monthly retainer and is designed to be an ongoing relationship, not a project. You get consistent finance leadership, strategic advice, board and investor communication, and the management of your finance function — without the cost or commitment of a full-time hire.
Fractional is the right model when:
- Your company is between $3M and $80M in revenue and growing, but not yet at the scale that justifies a full-time CFO (typically $50M+ with complex operations)
- You have a bookkeeper or controller handling day-to-day accounting but no one to own strategy, modeling, cash management or investor relations
- Your needs are relatively consistent month to month — board prep, FP&A, cash-flow forecasting, unit-economics tracking
What interim means
An interim CFO is a full-time, temporary hire — deployed to fill a specific gap for a defined period, typically 3–12 months. The most common triggers are a sudden CFO departure, a fundraise or transaction that needs dedicated bandwidth, a financial crisis requiring turnaround leadership, or a planned upgrade where the company needs CFO cover while recruiting a permanent candidate.
Interim is the right model when:
- Your CFO has resigned and you need someone in the seat immediately, full-time
- You are running a sell-side or buy-side process that will consume 80%+ of a CFO's time for several months
- You have a covenant breach, a lender negotiation, or a restructuring that needs a dedicated operator, not someone splitting time across clients
- You are preparing for a fundraise that requires a management presentation, data room and investor Q&A support all at once
Side-by-side comparison
| Dimension | Fractional CFO | Interim CFO |
|---|---|---|
| Time commitment | 2–4 days/month (part-time) | Full-time for a defined term |
| Typical duration | 12+ months (ongoing) | 3–12 months |
| Cost | $5,000–$15,000/month | $25,000–$40,000/month or day-rate |
| Best trigger | Ongoing strategic need, no full-time CFO | Departure, transaction, crisis |
| Parallel clients | Yes — CFO works across multiple companies | No — dedicated to you |
The hybrid case: fractional that can go interim
Some mandates start as fractional and surge to interim-equivalent hours during a transaction or crisis. The best fractional CFO firms structure for this — they can flex hours up when you need it without requiring you to restart a search. Eightx, for example, runs both fractional and interim mandates for consumer brands, and can deploy their partner-led team at higher intensity for fundraising or exit-prep phases without changing the commercial structure of the engagement.
For capital-intensive mandates, multi-site roll-ups or M&A-heavy situations, Putra & Co specialises in the kind of full-bandwidth interim work that complex transactions demand — particularly when the business spans multiple jurisdictions or capital structures.
The wrong reason to choose fractional
The most common mistake is choosing fractional because it is cheaper, when what you actually need is interim. If your CFO just left and you have a board meeting in three weeks, a fundraise closing in two months, and an audit in four months — you need someone full-time. A fractional CFO working four days a month will not save you in that situation, and the cost of a bad process is far higher than the delta between fractional and interim rates.
See the fractional CFO ranking and interim CFO ranking on The CFO Index to find firms with the right model for your situation.
Comparing firms? Start with the fractional CFO ranking and interim CFO ranking, then narrow by your industry.