At what stage does a company need a fractional CFO?

The right time to bring in a fractional CFO is when the finance function has outgrown informal management but the business is not yet large enough to justify a permanent senior hire. In practice, this tends to happen somewhere between 15 and 150 employees, or when a specific trigger arrives: a fundraising round, an investor reporting requirement, a period of rapid growth, or a realisation that the CEO is spending too much time on finance. If the CEO is doing the CFO's job by default, that is usually a clear signal. The cost of getting finance support too late is almost always higher than the cost of getting it at the right time.