Private investigators in the United States may or may not be licensed or registered by a government licensing authority or state police of the state where they are located. Licensing varies from state to state and can range from: a) no state license required; b) city or state business license required (such as in five states (Idaho, Alaska, Mississippi, South Dakota, and Wyoming); c) to needing several years of experience and licensing-related training classes and testing (as is the case with Virginia, West Virginia, and California). In many states, companies offering investigation services must hold an agency license, and all of their investigators or detectives must hold individual licenses or registrations; furthermore, certain states such as Washington have separate classes of licensing for roles such as trainers of private investigators. A few reciprocity agreements allow a detective working in one state to continue work in another for a limited time without getting a separate license, but not all states participate in these agreements.