It is very common for a staffing company to include credit check into their background verification process. The check itself usually costs ~$60 and is not commonly required by clients. It can be initiated, however, if the potential employer has reasons to believe that it is necessary. Again, such reasons are quite limited, it seems. Some government agencies have their own background investigation procedure, at which point they will notify an applicant on what information they need to provide. A basic check done by staffing agencies would normally include criminal check, diploma verification, and employment verification (references are called).