The core difference: backward vs forward
A controller makes sure the numbers are right. A CFO decides what to do about them.
| Controller | CFO | |
|---|---|---|
| Focus | Accuracy, the close, compliance | Strategy, forecasting, fundraising |
| Orientation | Backward (what happened) | Forward (what's next) |
| Owns | Books, AP/AR, monthly close, audit | Model, board reporting, capital |
| Reports to | CFO or founder | CEO / board |
| Fractional cost/mo | $2,000-$6,000 | $2,000-$15,000 |
When you need a controller
Your books are messy, the monthly close is late or unreliable, or you've outgrown a bookkeeper but the questions are still "are these numbers correct?" A controller cleans up the accounting foundation and produces financials you can trust. Without that foundation, a CFO has nothing reliable to build a forecast on.
When you need a CFO
The questions have shifted from "are these right?" to "what do they mean and what do we do?" — runway, pricing, unit economics, a fundraise, a hiring plan, a board that wants a model. That's CFO work. A fractional CFO at a $1M-$10M company gives you that strategic altitude without a $250,000+ full-time hire.
The honest answer for most companies
Most growing companies need both functions, not both full-time people. A common, cost-effective setup: a bookkeeper or part-time controller owns the close, and a fractional CFO sits above them owning strategy a few days a month. Start with whichever pain is louder — if you can't trust the numbers, fix that first; if you can't plan with them, hire up.