[protomyth]

IANAL

In some states, the only thing you can do is confirm the employee worked for you during a time range. Saying anything else is actionable by the former employee. It is really important to know the law in your locale.

It is actually safest legally just to say your company policy is to give dates only. If you took legal action against the employee (e.g. theft) then the new employer will find it on a background check. Their failure to do a background check is their fault.