Fractional CFOs are exceptional at the Series A stage. The work is structurally bounded, the cadence is monthly, and the value of senior judgement vastly outweighs the cost of part-time bandwidth. By Series C, the same arrangement starts to break — not because the people are wrong, but because the company has changed shape.
Why it works at A
At Series A you need someone who has built models for ten companies, sat through forty board meetings, and can tell you which metrics will matter to the next investor. You don't need them at their desk five days a week. You need their pattern recognition.
Why it stops working
- Audit cycle moves from optional to mandatory, with weekly auditor questions.
- Headcount crosses 80–100, requiring real FP&A cadence and partner business reviews.
- Treasury, FX, and working capital decisions become daily, not monthly.
- Investor reporting moves from quarterly board decks to live data rooms.
The clean handoff
We typically run a 90-day overlap with the incoming full-time CFO. Month one: shadow and document. Month two: co-own. Month three: the full-time CFO leads, fractional team becomes advisory. Done this way, the next close doesn't slip.