How do you evaluate interim CFO candidates?

The ability to rapidly get up to speed by quickly assessing actionable items, staff cabilities, and pending critical issues and reporting requirements to be immediately addressed.

When an interim CFO can identify weakness and suggest ways and means of improvement and or find alternative ways to better utilize the resources and maximize the output (increase efficiency). These could be things like cross functional duties (training) thereby limiting the time of a replacement and the work being done in the absence of such employee. Ensure all the necessary internal controls are in place. Evaluating payroll & benefits and come up with better/alternative solutions that may minimize such expenses etc.

Just curious why an interim CFO would have different eval criteria than a permanent one?

Although I agree with the quick-results advice offered above, take caution. An interim CFO who is not accountable for longer-term results may sacrifice those results in order to get a quick result.

Find someone who has a stake in those longer-term results as well.

I would want someone that shows an aptitude for engaging staff members. You want there to be some long term benefit to the engagement. If an interim, you want some knowledge to be left when he/she departs.

As with most any interim role, there's an expectation that someone else may be hired on a permanent basis, but that someone was needed right away. Because of this, the interim CFO might serve as the ideal change agent. The permanent CFO's job can be made a lot easier if re-organizations and other sensitive issues are addressed, at least in part, by an experienced interim CFO.